- First list item; no end tag
- Second list item; optional end tag included
- Third list item; no end tag
An attribute is included in the start tag only--never the end tag--and takes
the form Attribute-name="Attribute-value". The attribute value is delimited by
single or double quotes. The quotes are optional if the attribute value
consists solely of letters in the range A-Z and a-z, digits (0-9), hyphens
("-"), and periods (".").
Attribute names are case-insensitive, but attribute values may be
case-sensitive.
═══ 1.3.2.1. HTML 4.0 Attribute Values ═══
HTML 4.0 Attribute Values
There are various kinds of attribute values in HTML 4.0. This document
describes common types of values.
CDATA
Attribute values of type CDATA are made up of a sequence of characters that may
include entities. Line feeds are ignored while each carriage return and tab is
replaced with a space. Browsers may ignore leading and trailing whitespace
within the attribute value.
CDATA attribute values are typically case-sensitive, though this is not the
case with all attributes that take CDATA values.
ID and NAME
Attribute values of type ID and NAME must begin with a letter in the range A-Z
or a-z and may be followed by letters (A-Za-z), digits (0-9), hyphens ("-"),
underscores ("_"), colons (":"), and periods ("."). These values are
case-sensitive.
IDREF and IDREFS
IDREF and IDREFS values refer to values of other elements' ID attributes. An
IDREF value is a single ID while an IDREFS value is a space-separated list of
IDs. IDREF and IDREFS are case-sensitive.
Number
Number attribute values are numbers made of at least one digit in the range
0-9.
Text
Text attribute values are CDATA values intended to be human readable strings.
URI
URI attribute values are Uniform Resource Identifiers (URIs), as defined in the
URI Internet-Draft, a work-in-progress that is expected to replace RFC 1738 and
RFC 1808.
URI attribute values may include full URIs such as http://www.htmlhelp.com/. as
well as relative URIs such as foo.html and ../foo/.
While parts of a URI may be case-insensitive, in general URI values are
case-sensitive.
Color
Color attribute values give a color definition. The value can be any
hexadecimal number, specified according to the sRGB color space, or one of
sixteen color names. Hexadecimal numbers must be prefixed by a "#" character.
The case-insensitive color names and their sRGB values are as follows:
Color Name sRGB Value
Black #000000
Silver #C0C0C0
Gray #808080
White #FFFFFF
Maroon #800000
Red #FF0000
Purple #800080
Fuchsia #FF00FF
Green #008000
Lime #00FF00
Olive #808000
Yellow #FFFF00
Navy #000080
Blue #0000FF
Teal #008080
Aqua #00FFFF
Note that the hexadecimal form is better supported than the color names for the
color attributes of BODY.
Pixels
These attribute values are integers that represent a number of pixels.
Length
Length attribute values may be either an integer--interpreted as a number of
pixels--or a percentage of the horizontal or vertical space. The value 50%
means half the available space while 50 means 50 pixels.
MultiLength and MultiLengths
MultiLength attribute values may be an integer in pixels, a percentage of the
horizontal or vertical space, or a relative length expressed as i* where i is
an integer. In allotting space, a browser first allots pixel and percentage
lengths, then divides the remaining space among all elements with a relative
length. An element with a length of 3* will be allotted three times the space
of an element with length 1*. The value * is equivalent to 1* and is often used
to mean "fill the remaining space."
A MultiLengths value is a comma-separated list of MultiLength values.
ContentType and ContentTypes
These attribute values are content types (also known as media types or MIME
types) of a linked or embedded resource. Values of type ContentType give a
single content type while values of type ContentTypes give a comma-separated
list of content types. Content types are case-insensitive.
Commonly used content types include text/html, image/jpeg, model/vrml,
video/quicktime, application/java, text/css, and text/javascript. Many common
content types are registered at the IANA.
LanguageCode
Attribute values of type LanguageCode specify a language code according to RFC
1766. Examples of language codes include en for English, en-US for American
English, and ja for Japanese. Whitespace is not allowed in the language code,
which is case-insensitive.
Charset and Charsets
These attribute values specify character encodings of linked resources. Values
of type Charset give a single character encoding while values of type Charsets
give a space- and/or comma-separated list of character encodings. Character
encodings are case-insensitive.
Examples of character encodings include ISO-8859-1, SHIFT_JIS, and UTF-8. A
list of registered character encodings is available at the IANA.
Character
Character attribute values take a single Unicode character. The character may
be specified with an entity.
Datetime
Datetime attribute values give a date and time in the format
YYYY-MM-DDThh:mm:ssTZD where YYYY is a four-digit year, MM is a two-digit month
(01 through 12), DD is a two-digit day (01 through 31), hh is a two-digit
hour(00 through 23), mm is a two-digit minute (00 through 59), ss is a
two-digit second (00 through 59), and TZD is the time zone designator. Note
that the T separating the date from the time must appear literally and is
case-sensitive.
The time zone designator may be one of the following:
o Z (case-sensitive), which indicates Universal Coordinated Time (UTC,
basically the same as GMT);
o +hh:mm, the time ahead of UTC in hours and minutes;
o -hh:mm, the time behind UTC in hours and minutes.
If any of the two-digit components of the Datetime value are unknown, 00 should
be used.
LinkTypes
Attribute values of type LinkTypes give a space-separated list of link types. A
link type is case-insensitive and may not contain whitespace. Each link type
may be used any number of times in a given document.
While link types are case-insensitive, the Lynx browser will render LINK
elements with the same case as is given in the REL or REV attribute. Authors
should therefore be consistent in their case, and may wish to capitalize the
first letter while using lowercase for the rest.
The following link types are defined in HTML 4.0, though authors may use other
link types. The Made link type, widely used as to provide a contact link for the document
author, is notably missing from the list of link types defined in HTML 4.0.
o Alternate specifies an alternate version of the document. When used with the
LINK element's HREFLANG attribute, this value implies a translation of the
document. When used with LINK's MEDIA attribute, a media-specific version
(e.g., for printing) is implied.
o StyleSheet specifies an external style sheet for the document. This link type
can be combined with the Alternate link type to define an alternate style
sheet for the user to choose.
o Start specifies the first document in a collection.
o Next specifies the next document in a suggested sequence of reading. Browsers
such as WebTV will preload documents identified as "next" to improve the
perceived load time.
o Prev specifies the previous document in a suggested sequence of reading.
o Contents specifies a table of contents for the document.
o Index gives an index for the document.
o Glossary gives a glossary of terms used in the document.
o Copyright specifies a document with copyright information.
o Chapter specifies the chapter of a collection of documents.
o Section specifies the section of a collection of documents.
o Subsection specifies a subsection of a collection of documents.
o Appendix gives an appendix for the collection of documents.
o Help specifies a help document.
o Bookmark refers to a key related document. The TITLE attribute provides a
label for the bookmark.
MediaDesc
Attribute values of type MediaDesc are media descriptors--a comma-separated
list of media for which the linked resource is tailored. Media descriptors are
case-sensitive.
The following media descriptors are defined in HTML 4.0:
o screen (the default), for non-paged computer screens;
o tty, for fixed-pitch character grid displays (such as the display used by
Lynx);
o tv, for television-type devices with low resolution and limited
scrollability;
o projection, for projectors;
o handheld, for handheld devices (characterized by a small, monochrome display
and limited bandwidth);
o print, for output to a printer;
o braille, for braille tactile feedback devices;
o aural, for speech synthesizers;
o all, for all devices.
Script
Script attribute values are client-side scripts, typically a function call or a
few short statements. The value may contain entities (e.g., ").
StyleSheet
Attribute values of type StyleSheet are style sheet data. The value may contain
entities.
FrameTarget
Attribute values of type FrameTarget must begin with a letter in the range A-Z
or a-z, with the exception of the following special values that begin with an
underscore:
o _blank renders the link in a new, unnamed window
o _self renders the link in the current frame (useful for overriding a BASE
TARGET)
o _parent renders the link in the immediate FRAMESET parent
o _top renders the link in the full, unframed window
═══ 1.3.2.2. HTML 4.0 Common Attributes ═══
HTML 4.0 Common Attributes
A number of attributes in HTML 4.0 are common to most elements. These
attributes are divided into core attributes, internationalization attributes,
and scripting events.
Core Attributes
ID
The ID attribute uniquely identifies an element within a document. No two
elements can have the same ID value in a single document. The attribute's value
must begin with a letter in the range A-Z or a-z and may be followed by letters
(A-Za-z), digits (0-9), hyphens ("-"), underscores ("_"), colons (":"), and
periods (".").
The following example uses the ID attribute to identify each of the first two
paragraphs of a document:
My first paragraph.
My second paragaph.
The paragraphs in the example could have style rules associated with them through their ID attributes. The following Cascading Style Sheet defines unique colors for the two paragraphs: P#firstp { color: navy; background: transparent } P#secondp { color: black; background: transparent } The paragraphs in the initial example could also be used as a target anchor for links:See the opening paragraph for more information.
Note that most browsers do not support the ID attribute for link anchors. For current browsers, authors should use ... within the element instead of ID. Since ID and NAME share the same name space, authors cannot use the same value for an ID attribute and a NAME attribute in the same document. Also note that while NAME may contain entities, the ID attribute value may not. CLASS The CLASS attribute specifies the element to be a member of one or more classes. Classes allow authors to define specific kinds of a given element. For example, an author could use when giving Java code and when giving Perl code.
Unlike with the ID attribute, any number of elements can share the same class.
An element may also belong to multiple classes; the CLASS attribute value is a
space-separated list of class names.
Note that most current browsers do not support multiple classes. Such browsers
typically ignore a CLASS attribute that specifies multiple classes.
The CLASS attribute is particularly useful when combined with style sheets .
For example, consider the following navigation bar:
This example's use of the CLASS attribute allows style rules to easily be
added. The following Cascading Style Sheet suggests a presentation for the
preceding example:
.navbar {
margin-top: 2em;
padding-top: 1em;
border-top: solid thin navy
}
.navbar IMG { float: right }
@media print {
.navbar { display: none }
}
STYLE
The STYLE attribute allows authors to specify style rules inline for a single
occurrence of an element. An example follows:
A popular font for on-screen reading is
Verdana.
When the STYLE attribute is used, a default style sheet language must be
specified for the document by setting the Content-Style-Type HTTP header to the
media type of the style sheet language. The previous example could use the
following META element in the document's HEAD:
In most cases, use of the CLASS or ID attributes is a better choice than using
STYLE since ID and CLASS can be selectively applied to different media and
since they provide a separation of content and presentation that often
simplifies maintenance.
TITLE
The TITLE attribute provides a title for an element and is commonly implemented
as a "tooltip" on visual browsers, though many browsers lack support for TITLE.
The attribute is most useful with A, LINK, IMG, and OBJECT elements, where it
provides a title for the linked or embedded resource. Some examples follow:
o
liam@htmlhelp.com
o
CGI.pm
o
o
TITLE is also helpful with the ABBR and ACRONYM elements to provide the long
form of the abbreviation. Examples:
o He weighs 180 lbs.
o PQ
o NATO
Internationalization Attributes
LANG
The LANG attribute specifies the language of an element's attribute values and
its content, including all contained elements that do not specify their own
LANG attribute. While the LANG attribute is not widely supported, its use may
help search engines index a document by its language while allowing speech
synthesizers to use language-dependent pronunciation rules. As well, visual
browsers can use the language's proper quotation marks when rendering the Q
element.
The attribute value is case-insensitive, and should be specified according to
RFC 1766; examples include en for English, en-US for American English, and ja
for Japanese. Whitespace is not allowed in the language code.
Use of the LANG attribute also allows authors to easily change the style of
text depending on the language. For example, a bilingual document may have one
language in italics if rendered visually or a different voice if rendered
aurally. The HTML of such a document might be as follows:
Welcome - Bienvenue
Welcome -
Bienvenue
This paragraph is in English.
Ce paragraphe est en franЗais.
...
A document's primary language may be set using the LANG attribute on the HTML
element, or, alternatively, by using the Content-Language HTTP header.
DIR
The DIR attribute specifies the directionality of text--left-to-right (DIR=ltr,
the default) or right-to-left (DIR=rtl). Characters in Unicode are assigned a
directionality, left-to-right or right-to-left, to allow the text to be
rendered properly. For example, while English characters are presented
left-to-right, Hebrew characters are presented right-to-left.
Unicode defines a bidirectional algorithm that must be applied whenever a
document contains right-to-left characters. While this algorithm usually gives
the proper presentation, some situations leave directionally neutral text and
require the DIR attribute to specify the base directionality.
Text is often directionally neutral when there are multiple embeddings of
content with a different directionality. For example, an English sentence that
contains a Hebrew phrase that contains an English quotation would require the
DIR attribute to define the directionality of the Hebrew phrase. The Hebrew
phrase, including the English quotation, should be contained within a SPAN
element with DIR=rtl.
Common Scripting Events
A number of attributes that define client-side scripting events are common to
most elements. The attribute value is a script--typically a function call or a
few short statements--that is executed when the event occurs. The value may
contain entities (e.g., " ).
The following example features JavaScript code to handle two events of a submit
button, giving the user a reminder in the status bar when the mouse moves over
the button and clearing the status bar when the mouse moves away. Note that the
attribute values are delimited by single quotes since double quotes are used
within them.
When an event attribute is used, a default scripting language must be specified
for the document by setting the Content-Script-Type HTTP header to the media
type of the scripting language. The previous example could use the following
META element in the document's HEAD:
The common event attributes are device-dependent and largely tailored for the
graphical user interface. The available events are as follows:
o ONCLICK, when the mouse button is clicked on an element;
o ONDBLCLICK, when the mouse button is double-clicked on an element;
o ONMOUSEDOWN, when the mouse button is pressed over an element;
o ONMOUSEUP, when the mouse button is released over an element;
o ONMOUSEOVER, when the mouse is moved onto an element;
o ONMOUSEMOVE, when the mouse is moved while over an element;
o ONMOUSEOUT, when the mouse is moved away from an element;
o ONKEYPRESS, when a key is pressed and released over an element;
o ONKEYDOWN, when a key is pressed down over an element;
o ONKEYUP, when a key is released over an element.
═══ 1.3.2.2.1. Core Attributes ═══
Core Attributes
ID
The ID attribute uniquely identifies an element within a document. No two
elements can have the same ID value in a single document. The attribute's value
must begin with a letter in the range A-Z or a-z and may be followed by letters
(A-Za-z), digits (0-9), hyphens ("-"), underscores ("_"), colons (":"), and
periods (".").
The following example uses the ID attribute to identify each of the first two
paragraphs of a document:
My first paragraph.
My second paragaph.
The paragraphs in the example could have style rules associated with them
through their ID attributes. The following Cascading Style Sheet defines unique
colors for the two paragraphs:
P#firstp {
color: navy;
background: transparent
}
P#secondp {
color: black;
background: transparent
}
The paragraphs in the initial example could also be used as a target anchor for
links:
See the opening paragraph
for more information.
Note that most browsers do not support the ID attribute for link anchors. For
current browsers, authors should use ... within the element instead
of ID.
Since ID and NAME share the same name space, authors cannot use the same value
for an ID attribute and a NAME attribute in the same document. Also note that
while NAME may contain entities, the ID attribute value may not.
CLASS
The CLASS attribute specifies the element to be a member of one or more
classes. Classes allow authors to define specific kinds of a given element. For
example, an author could use when giving Java code and when giving Perl code.
Unlike with the ID attribute, any number of elements can share the same class.
An element may also belong to multiple classes; the CLASS attribute value is a
space-separated list of class names.
Note that most current browsers do not support multiple classes. Such browsers
typically ignore a CLASS attribute that specifies multiple classes.
The CLASS attribute is particularly useful when combined with style sheets .
For example, consider the following navigation bar:
This example's use of the CLASS attribute allows style rules to easily be
added. The following Cascading Style Sheet suggests a presentation for the
preceding example:
.navbar {
margin-top: 2em;
padding-top: 1em;
border-top: solid thin navy
}
.navbar IMG { float: right }
@media print {
.navbar { display: none }
}
STYLE
The STYLE attribute allows authors to specify style rules inline for a single
occurrence of an element. An example follows:
A popular font for on-screen reading is
Verdana.
When the STYLE attribute is used, a default style sheet language must be
specified for the document by setting the Content-Style-Type HTTP header to the
media type of the style sheet language. The previous example could use the
following META element in the document's HEAD:
In most cases, use of the CLASS or ID attributes is a better choice than using
STYLE since ID and CLASS can be selectively applied to different media and
since they provide a separation of content and presentation that often
simplifies maintenance.
TITLE
The TITLE attribute provides a title for an element and is commonly implemented
as a "tooltip" on visual browsers, though many browsers lack support for TITLE.
The attribute is most useful with A, LINK, IMG, and OBJECT elements, where it
provides a title for the linked or embedded resource. Some examples follow:
o
liam@htmlhelp.com
o
CGI.pm
o
o
TITLE is also helpful with the ABBR and ACRONYM elements to provide the long
form of the abbreviation. Examples:
o He weighs 180 lbs.
o PQ
o NATO
═══ 1.3.2.2.2. Internationalization Attributes ═══
Internationalization Attributes
LANG
The LANG attribute specifies the language of an element's attribute values and
its content, including all contained elements that do not specify their own
LANG attribute. While the LANG attribute is not widely supported, its use may
help search engines index a document by its language while allowing speech
synthesizers to use language-dependent pronunciation rules. As well, visual
browsers can use the language's proper quotation marks when rendering the Q
element.
The attribute value is case-insensitive, and should be specified according to
RFC 1766; examples include en for English, en-US for American English, and ja
for Japanese. Whitespace is not allowed in the language code.
Use of the LANG attribute also allows authors to easily change the style of
text depending on the language. For example, a bilingual document may have one
language in italics if rendered visually or a different voice if rendered
aurally. The HTML of such a document might be as follows:
Welcome - Bienvenue
Welcome -
Bienvenue
This paragraph is in English.
Ce paragraphe est en franЗais.
...
A document's primary language may be set using the LANG attribute on the HTML
element, or, alternatively, by using the Content-Language HTTP header.
DIR
The DIR attribute specifies the directionality of text--left-to-right (DIR=ltr,
the default) or right-to-left (DIR=rtl). Characters in Unicode are assigned a
directionality, left-to-right or right-to-left, to allow the text to be
rendered properly. For example, while English characters are presented
left-to-right, Hebrew characters are presented right-to-left.
Unicode defines a bidirectional algorithm that must be applied whenever a
document contains right-to-left characters. While this algorithm usually gives
the proper presentation, some situations leave directionally neutral text and
require the DIR attribute to specify the base directionality.
Text is often directionally neutral when there are multiple embeddings of
content with a different directionality. For example, an English sentence that
contains a Hebrew phrase that contains an English quotation would require the
DIR attribute to define the directionality of the Hebrew phrase. The Hebrew
phrase, including the English quotation, should be contained within a SPAN
element with DIR=rtl.
═══ 1.3.2.2.3. Common Scripting Events ═══
Common Scripting Events
A number of attributes that define client-side scripting events are common to
most elements. The attribute value is a script--typically a function call or a
few short statements--that is executed when the event occurs. The value may
contain entities (e.g., " ).
The following example features JavaScript code to handle two events of a submit
button, giving the user a reminder in the status bar when the mouse moves over
the button and clearing the status bar when the mouse moves away. Note that the
attribute values are delimited by single quotes since double quotes are used
within them.
When an event attribute is used, a default scripting language must be specified
for the document by setting the Content-Script-Type HTTP header to the media
type of the scripting language. The previous example could use the following
META element in the document's HEAD:
The common event attributes are device-dependent and largely tailored for the
graphical user interface. The available events are as follows:
o ONCLICK, when the mouse button is clicked on an element;
o ONDBLCLICK, when the mouse button is double-clicked on an element;
o ONMOUSEDOWN, when the mouse button is pressed over an element;
o ONMOUSEUP, when the mouse button is released over an element;
o ONMOUSEOVER, when the mouse is moved onto an element;
o ONMOUSEMOVE, when the mouse is moved while over an element;
o ONMOUSEOUT, when the mouse is moved away from an element;
o ONKEYPRESS, when a key is pressed and released over an element;
o ONKEYDOWN, when a key is pressed down over an element;
o ONKEYUP, when a key is released over an element.
═══ 1.3.3. Special Characters ═══
Special Characters
Certain characters in HTML are reserved for use as markup and must be escaped
to appear literally. The "<" character may be represented with an entity, <.
Similarly, ">" is escaped as >, and "&" is escaped as &. If an attribute
value contains a double quotation mark and is delimited by double quotation
marks, then the quote should be escaped as ".
Other entities exist for special characters that cannot easily be entered with
some keyboards. For example, the copyright symbol ("╕") may be represented with
the entity ©. See the Entities section for a complete list of HTML 4.0
entities.
As an alternative to entities, authors may also use numeric character
references. Any character may be represented by a numeric character reference
based on its "code position" in Unicode. For example, one could use © for
the copyright symbol or ا for the Arabic letter ALEF.
═══ 1.3.4. Comments ═══
Comments
Comments in HTML have a complicated syntax that can be simplified by following
this rule: Begin a comment with "", and do not use "--"
within the comment.
═══ 1.3.5. A Complete HTML 4.0 Document ═══
A Complete HTML 4.0 Document
An HTML 4.0 document begins with a DOCTYPE declaration that declares the
version of HTML to which the document conforms. The HTML element follows and
contains the HEAD and BODY. The HEAD contains information about the document,
such as its title and keywords, while the BODY contains the actual content of
the document, made up of block-level elements and inline elements. A basic
HTML 4.0 document takes on the following form:
The document title
Main heading
A paragraph.
Another paragraph.
- A list item.
- Another list item.
In a Frameset document, the FRAMESET element replaces the BODY element.
═══ 1.3.6. Validating your HTML ═══
Validating your HTML
Each HTML document should be validated to check for errors such as missing
quotation marks (My photo album
Picture of me
Auld Lang Syne (5 kB MIDI)
Section 2
liam@htmlhelp.com
Web Design Group
ISO 639
The value of the HREF attribute is the URI of the link. The TYPE attribute
can be used to specify the Internet media type of the link, allowing browsers
to avoid fetching a resource that they cannot handle.
The TITLE attribute can be used to briefly describe the contents of the link
and is rendered as a "tooltip" by some visual browsers. With mailto links,
some browsers use the TITLE attribute value as a subject for the e-mail
message.
The content of an A element used as a link should be as context-free as
possible. In other words, a user should be able to pull all A elements from a
document and still have an idea what lies behind each link. Link text that
contains Click here or simply here is extremely bad form.
The TARGET attribute is used with frames to specify in which frame the link
should be rendered. If no frame with such a name exists, the link is rendered
in a new window unless overridden by the user. Special frame names begin with
an underscore:
o _blank renders the link in a new, unnamed window
o _self renders the link in the current frame (useful for overriding a BASE
TARGET)
o _parent renders the link in the immediate FRAMESET parent
o _top renders the link in the full, unframed window
The optional HREFLANG and CHARSET attributes give the language and character
encoding, respectively, of the link. The language should be specified
according to RFC 1766; examples include en for English, en-US for American
English, and ja for Japanese. Examples of character encodings include
ISO-8859-1, SHIFT_JIS, and UTF-8.
The ACCESSKEY attribute specifies a single Unicode character as a shortcut key
for following the link. Entities (e.g. é) may be used as the ACCESSKEY
value.
The TABINDEX attribute specifies a number between 0 and 32767 to indicate the
tabbing order of the element. An anchor with TABINDEX=0 or no TABINDEX
attribute will be visited after any elements with a positive TABINDEX. Among
positive TABINDEX values, the lower number receives focus first. In the case
of a tie, the element appearing first in the HTML document takes precedence.
The REL and REV attributes define relationships between an anchor and the
linked resource. REL defines a link relationship from the current document to
the linked document while REV defines a relationship in the opposite
direction. For example,
...
indicates that foo.html is a glossary for the current document while
...
indicates that the current document is a subsection of bar.html. The value of
the REL and REV attributes is a space-separated list of link types.
The NAME attribute defines a destination for a link. For example, a document
containing
My Heading
defines a link destination named "foo" at the indicated heading. One could
then use HREF="#foo" in an A element within the same document or
HREF="somedoc.html#foo" from within another document.
An A element cannot contain another A element, so one must be careful that
named anchors do not contain link anchors. Authors can use both the NAME and
HREF attributes in a single A element to avoid this problem.
HTML 4.0's ID attribute is intended to eliminate the need for A NAME. The ID
attribute can be used with almost any element to define a link destination, so
that the following could be used in place of the previous example:
My heading
However, browser support for ID link destinations is very poor, so A NAME
will be needed for quite awhile.
NAME and ID values must be unique in any document, and different values must
differ by more than just the case. Values must begin with a letter in the
range A-Z or a-z, and may be followed by A-Z, a-z, 0-9, hyphens, underscores,
colons, or periods. When linking to a named anchor, the name is treated as
case sensitive.
The SHAPE and COORDS attributes of A can be used to create client-side image
maps via the OBJECT element. The default SHAPE value is rect, which
defines a rectangular region using COORDS="left, top, right, bottom". Other
SHAPE values are
o default, which specifies the entire image;
o circle, which specifies a circular region using COORDS="center-x, center-y,
radius";
o poly, which specifies a polygonal region using COORDS="x1, y1, x2, y2, ...,
xN, yN".
Coordinate values are relative to the top left corner of the object and may be
expressed as pixels or percentages. A percentage radius value for circular
regions is calculated relative to the smaller of the object's width and height.
If two or more regions overlap, the earliest specified region takes precedence.
In addition to the core events common to most elements, A accepts the
following event attributes for client-side scripting:
o ONFOCUS, when the link receives focus;
o ONBLUR, when the link loses focus.
═══ 1.5.2. ABBR - Abbreviation ═══
ABBR - Abbreviation
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The ABBR element is used to markup abbreviations. The TITLE attribute is
useful in conjunction with ABBR to give the long form of the abbreviation,
allowing visual browsers to provide the long form as a "tooltip". If the short
form is a pronounceable word, the ACRONYM element should be used instead of
ABBR.
Examples:
U.N.
He weighs 180 lbs.
PQ
NATO
Some short forms, such as "SQL" and "URL," are pronounced as words by some but
pronounced letter-by-letter by others. In such cases, the ABBR element should
be favored over ACRONYM. A style sheet could be used to suggest the aural
rendering. For example, one could use
URL
with the following CSS2 style sheet:
abbr[title="Uniform Resource Locator"] { speak: spell-out }
═══ 1.5.3. ACRONYM - Acronym ═══
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The ACRONYM element is used to markup acronyms. The TITLE attribute is
useful in conjunction with ACRONYM to give the long form of the acronym,
allowing visual browsers to provide the long form as a "tooltip". Examples:
NATO
radar
FBI
Unlike other kinds of abbreviations, acronyms are pronounceable words, though
in some cases the pronunciation is strictly a presentation issue. For example,
"SQL" and "URL" are pronounced as words by some people and pronounced
letter-by-letter by others. In such cases, authors should use the ABBR
element, possibly with a style sheet rule specifying the pronunciation for
aural rendering.
═══ 1.5.4. ADDRESS - Address ═══
ADDRESS - Contact Information
Syntax
...
Attribute Specifications
o common attributes
Contents
o In HTML 4.0 Strict: inline elements
o In HTML 4.0 Transitional: inline elements, P
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The ADDRESS element provides contact information for a document or part of a
document. Information provided by ADDRESS may include the names of the
document's maintainers, links to the maintainers' Web pages, e-mail addresses
for feedback, postal addresses, phone numbers, and so on. The ADDRESS element
is not appropriate for all postal and e-mail addresses; it should be reserved
for providing such information about the contact people for the document.
The following example, most appropriate at the end of a document, gives contact
information about the maintainer:
Maintained by Liam Quinn <
liam@htmlhelp.com>
ADDRESS can also be used to provide contact information for a portion of a
document, typically a form. The next example gives users contact information
to use in conjunction with an order form:
═══ 1.5.5. APPLET - Java applet ═══
APPLET - Java Applet
Syntax
Attribute Specifications
o CODE= CDATA (class file)
o CODEBASE= URI (base URI for class files)
o WIDTH= Length (applet width)
o HEIGHT= Length (applet height)
o ARCHIVE= CDATA (archive files)
o OBJECT= CDATA (serialized applet)
o NAME= CDATA (name for inter-applet communication)
o ALT= Text (alternate text)
o ALIGN=[ top | middle | bottom | left | right ] (applet alignment)
o HSPACE= Pixels (horizontal gutter)
o VSPACE= Pixels (vertical gutter)
o common attributes
Contents
PARAM elements followed by block-level elements and/or inline
elements
Contained in
Inline elements, block-level elements except PRE
The APPLET element is used to embed Java applets. It has been deprecated in
HTML 4.0 in favor of the more generalized OBJECT element. However, since the
few browsers that support OBJECT do so with significant bugs, APPLET is
currently a more reliable method of embedding Java applets.
APPLET's CODE attribute specifies the name of the class file that contains the
compiled Applet subclass. The value is relative to the URI specified in the
CODEBASE attribute, or to the HTML document's base URI if the CODEBASE
attribute is not given.
The required WIDTH and HEIGHT attributes define the dimensions of the applet.
The value may be given in pixels or as a percentage of the parent element's
width or height.
The ALT attribute can be used to give alternate text for browsers that
recognize the APPLET element but do not support Java or do not have Java
enabled. Authors can also give alternate content between the start and end
tags of the APPLET element--a better method than using the ALT attribute
since it allows authors to include HTML markup in the alternate content and
also works with pre- HTML 3.2 browsers that do not support APPLET.
An APPLET may contain PARAM elements to define applet-specific parameters.
PARAM elements should be specified before any other content of the APPLET
element. In the following example, a decorative Java applet takes two
parameters. The APPLET contains an animated GIF as an alternative for non-Java
browsers.
The ARCHIVE attribute can specify a comma-separated list of archived files
(either absolute URIs or URIs relative to the CODEBASE), allowing the browser
to download many files with a single connection and hence decreasing the total
download time. The standard archive format for Java files is JAR. JAR files
can be created with the jar tool included with the Java Development Kit 1.1
and up.
Note that some browsers do not support the ARCHIVE attribute, so all necessary
files should be available unarchived as well. Other browsers only support a
single URI as the ARCHIVE value.
The OBJECT attribute specifies a serialized (saved) representation of an
applet. The CODE attribute should not be used if and only if the OBJECT
attribute is specified. When the applet is deserialized, its init() method is
not invoked, but its start() method is. Sun recommends restraint in using
this poorly supported feature.
The ALIGN attribute specifies the alignment of the applet. The values top,
middle, and bottom specify the applet's position with respect to surrounding
content on its left and right.
ALIGN=middle aligns the center of the applet with the current baseline. To
center the applet horizontally on the page, place the applet in a centered
block, e.g.,
The other ALIGN values, left and right, specify a floating applet; the
applet is placed at the left or right margin and content flows around it. To
place content below the applet, use
as appropriate.
The vertical-align and float properties of Cascading Style Sheets provide
more flexible methods of aligning applets.
The HSPACE and VSPACE attributes allow an author to suggest horizontal
gutters and vertical gutters, respectively, around the applet. The value must
be in pixels and applies to both sides of the applet. Style sheets provide
more flexibility in specifying the space around applets.
═══ 1.5.6. AREA - Image map region ═══
AREA - Image Map Region
Syntax
Attribute Specifications
o SHAPE=[ rect | circle | poly | default ] (shape of region)
o COORDS=Coords (coordinates of region)
o HREF= URI (linked resource)
o TARGET= FrameTarget (frame to render link in)
o NOHREF (inactive region)
o ALT= Text (alternate text)
o TABINDEX= Number (position in tabbing order)
o ONFOCUS= Script (region received focus)
o ONBLUR= Script (region lost focus)
o common attributes
Contents
Empty
Contained in
MAP
The AREA element defines a map region in a client-side image map. Each map
region is a piece of the image with a different action when clicked.
The SHAPE and COORDS attributes of AREA specify what part of the image is
included in the region. The default SHAPE value is rect, which defines a
rectangular region using COORDS="left, top, right, bottom". Other SHAPE
values are
o default, which specifies the entire image;
o circle, which specifies a circular region using COORDS="center-x, center-y,
radius";
o poly, which specifies a polygonal region using COORDS="x1, y1, x2, y2, ...,
xN, yN".
Coordinate values are relative to the top left corner of the object and may be
expressed as pixels or percentages. A percentage radius value for circular
regions is calculated relative to the smaller of the object's width and height.
If two or more regions overlap, the earliest specified region takes precedence.
The HREF attribute specifies a link to another resource, such as an HTML
document or a JPEG image. The TITLE attribute can be used to briefly
describe the contents of the link and is rendered as a "tooltip" by some visual
browsers. The boolean NOHREF attribute indicates that the region has no link.
The required ALT attribute provides alternate text for those not loading
images. Effective ALT text should generally give the function of the map
region rather than a description of the region. For example, ALT="WDG Home"
or ALT="Web Design Group" would be more appropriate than ALT="WDG Logo" for a
map region whose link went to the WDG home page. Good ALT text is crucial to
the document's accessibility for the significant portion of users who do not
load images.
The TARGET attribute is used with frames to specify in which frame the link
should be rendered. If no frame with such a name exists, the link is rendered
in a new window unless overridden by the user. Special frame names begin with
an underscore:
o _blank renders the link in a new, unnamed window
o _self renders the link in the current frame (useful for overriding a BASE
TARGET)
o _parent renders the link in the immediate FRAMESET parent
o _top renders the link in the full, unframed window
The ACCESSKEY attribute specifies a single Unicode character as a shortcut key
for following the link. Entities (e.g. é) may be used as the ACCESSKEY
value.
The TABINDEX attribute specifies a number between 0 and 32767 to indicate the
tabbing order of the map region. A region with TABINDEX=0 or no TABINDEX
attribute will be visited after any elements with a positive TABINDEX. Among
positive TABINDEX values, the lower number receives focus first. In the case
of a tie, the element appearing first in the HTML document takes precedence.
In addition to the core events common to most elements, AREA accepts the
following event attributes for client-side scripting:
o ONFOCUS, when the region receives focus;
o ONBLUR, when the region loses focus.
═══ 1.5.7. B - Bold Text ═══
B - Bold Text
Syntax
...
Attribute Specifications
common attributes"
Contents
Inline elements
Contained in
Inline elements, block-level elements
The B element suggests that text be rendered as bold text. In most cases, use
of a phrase element such as STRONG is more appropriate since such elements
express the meaning of the text more clearly.
The B element is a suitable choice for marking a structure for which no phrase
element exists. For example, vectors in mathematics have no structural element
in HTML 4.0, but bold text is often an appropriate visual rendering:
If two vectors v and
w are orthogonal, we write
v ⊥ w.
Note the use of the CLASS attribute to add structural significance to the B
elements. This allows greater flexibility when applying style sheets to
different kinds of bold text.
═══ 1.5.8. BASE - Document base URI ═══
BASE - Document Base URI
Syntax
...
Attribute Specifications
o CITE= URI (source of quotation)
o common attributes
Contents
o In HTML 4.0 Strict: one or more block-level elements or SCRIPT
o In HTML 4.0 Transitional: inline elements or block-level elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The BLOCKQUOTE element defines a block quotation. Unlike inline quotations,
block quotations may contain block-level elements such as P and TABLE, but
BLOCKQUOTE may not be contained within a paragraph or inline element.
The optional CITE attribute of BLOCKQUOTE provides the URI of the source of
the quotation. This attribute, not widely supported among browsers, allows
readers to verify the authenticity of the quotation and also find related
information.
The content of the BLOCKQUOTE element should be contained within other
block-level elements, typically P. The following example features a quotation
that includes multiple paragraphs and its own block quotation:
He pointed his finger in friendly jest and went over to the parapet, laughing
to himself. Stephen Dedalus stepped up, followed him wearily half way and
sat down on the edge of the gunrest, watching him still as he propped his mirror
on the parapet, dipped the brush in the bowl and lathered cheeks and
neck.
Buck Mulligan's gay voice went on.
My name is absurd too: Malachi Mulligan, two dactyls.
But it has a Hellenic ring, hasn't it? Tripping and sunny like the buck
himself. We must go to Athens. Will you come if I can get the aunt to
fork out twenty quid?
Authors should not use BLOCKQUOTE for unquoted material just to achieve a
block indentation in common visual browsers. With the rise of style sheets,
such misuse of BLOCKQUOTE will become less reliable while also reducing the
author's ability to fully exploit the power of style sheets. Cascading Style
Sheets provide the margin-left property to indent a block.
═══ 1.5.13. BODY - Document body ═══
BODY - Document Body
Syntax
...
Attribute Specifications
o BACKGROUND= URI (background image for document)
o BGCOLOR= Color (background color for document)
o TEXT= Color (text color for document)
o LINK= Color (link color for document)
o VLINK= Color (visited link color for document)
o ALINK= Color (active link color for document)
o ONLOAD= Script (document has been loaded)
o ONUNLOAD= Script (document has been exited)
o common attributes
Contents
o In HTML 4.0 Strict: one or more block-level elements or SCRIPT, INS, DEL
o In HTML 4.0 Transitional: inline elements, block-level elements, INS, DEL
Contained in
o In HTML 4.0 Strict or Transitional: HTML
o In HTML 4.0 Frameset: NOFRAMES
The BODY element contains the document body. BODY is required in non-frames
documents, but its start and end tags are always optional. In frames
documents, BODY must be contained within the NOFRAMES element, if NOFRAMES
is used.
The BODY element contains the document's content. The content should be
contained within block-level elements or SCRIPT elements, though HTML 4.0
Transitional also allows inline elements directly within BODY.
BODY takes a number of attributes for specifying the background and colors of
the document on visual browsers. These attributes are deprecated in HTML 4.0
in favor of style sheets, which provide greater flexibility in suggesting the
presentation of a document. BGCOLOR suggests a background color, TEXT
suggests a text color, LINK suggests a link color, VLINK suggests a visited
link color, and ACTIVE suggests an active link color (when the link is
selected). If one of these attributes is given, then all of them should be
included to ensure that the user's chosen colors do not interfere with those
suggested in the tag. Authors should not rely on the specified colors
being used since browsers allow these colors to be overridden by the user.
The BACKGROUND attribute suggests a background image for tiling on the
document canvas. To help ensure a readable document, the BGCOLOR, TEXT, LINK,
VLINK, and ALINK attributes should always be included when BACKGROUND is
given. The BGCOLOR will be used for those not loading images.
Style sheets allow more flexibility in suggesting a background image,
including the ability to specify the position of the image, how the image is
tiled, and whether the image should scroll with the document.
In addition to the core events common to most elements, BODY accepts the
following event attributes for client-side scripting:
o ONLOAD, when the document has been loaded;
o ONUNLOAD, when the document is exited.
═══ 1.5.14. BR - Line break ═══
BR - Line Break
Syntax
Attribute Specifications
o CLEAR=[ left | all | right | none ] (clear floating objects)
o core attributes
Contents
Empty
Contained in
Inline elements, block-level elements
The BR element forces a break in the current line of text. BR can be useful
in formatting addresses within the ADDRESS element, but it is often misused
to break lines of text in a paragraph or table cell when it looks "nice" to the
author. This usually results in an awkward presentation when viewed with a
font size other than that used by the author.
The CLEAR attribute of BR is used to move below floating objects (typically
images or tables). In the following example, the second paragraph should be
rendered below the floating image:
Toronto is the largest city in Canada and the fourth largest in North
America.
The city is highly multicultural, with over 80 ethnic
communities from Africa, Asia, and Europe...
Style sheets provide more flexibility in controlling text flow around objects
and eliminate the need to use BR for this purpose since CSS1's clear property
can be applied to any element (such as the second paragraph in the preceding
example).
═══ 1.5.15. BUTTON - Button ═══
BUTTON - Button
Syntax
Attribute Specifications
o NAME= CDATA (key in submitted form)
o VALUE= CDATA (value in submitted form)
o TYPE=[ submit | reset | button ] (type of button)
o DISABLED (disable button)
o ACCESSKEY= Character (shortcut key)
o TABINDEX= Number (position in tabbing order)
o ONFOCUS= Script (element received focus)
o ONBLUR= Script (element lost focus)
o common attributes
Contents
o Inline elements except A, INPUT, SELECT, TEXTAREA, LABEL, BUTTON, and
IFRAME
o Block-level elements except FORM, ISINDEX, and FIELDSET
Contained in
Block-level elements, inline elements except BUTTON
The BUTTON element defines a submit button, reset button, or push button.
Authors can also use INPUT to specify these buttons, but the BUTTON element
allows richer labels, including images and emphasis. However, BUTTON is new
in HTML 4.0 and poorly supported among current browsers, so INPUT is a more
reliable choice at this time.
The TYPE attribute of BUTTON specifies the kind of button and takes the value
submit (the default), reset, or button. The NAME and VALUE attributes
determine the name/value pair sent to the server when a submit button is
pushed. These attributes allow authors to provide multiple submit buttons and
have the form handler take a different action depending on the submit button
used.
Some examples of BUTTON follow:
The ACCESSKEY attribute, used throughout the preceding examples, specifies a
single Unicode character as a shortcut key for pressing the button. Entities
(e.g. é) may be used as the ACCESSKEY value.
The boolean DISABLED attribute makes the BUTTON element unavailable. The user
is unable to push the button, the button cannot receive focus, and the button
is skipped when navigating the document by tabbing.
The TABINDEX attribute specifies a number between 0 and 32767 to indicate the
tabbing order of the button. A BUTTON element with TABINDEX=0 or no TABINDEX
attribute will be visited after any elements with a positive TABINDEX. Among
positive TABINDEX values, the lower number receives focus first. In the case
of a tie, the element appearing first in the HTML document takes precedence.
The BUTTON element also takes a number of attributes to specify client-side
scripting actions for various events. In addition to the core events common
to most elements, BUTTON accepts the following event attributes:
o ONFOCUS, when the element receives focus;
o ONBLUR, when the element loses focus.
═══ 1.5.16. CAPTION - Table caption ═══
CAPTION - Table Caption
Syntax
...
Attribute Specifications
o ALIGN=[ top | bottom | left | right ] (caption alignment)
o common attributes
Contents
Inline elements
Contained in
TABLE
The CAPTION element defines a table caption. When used, CAPTION must be the
first element in the TABLE. Only inline elements (e.g., STRONG) may be used
within CAPTION.
A good caption should provide a short heading for the table. For simple
tables, the caption can also act as an adequate summary, but for more complex
tables, authors should supplement the CAPTION with a full summary, either
through TABLE's SUMMARY attribute or within a paragraph outside of the
TABLE. The following example features a simple table where the CAPTION
provides a heading and an adequate table summary:
Common Usenet Abbreviations
Abbreviation
Long Form
AFAIK
As Far As I Know
IMHO
In My Humble Opinion
OTOH
On The Other Hand
The next example uses TABLE's SUMMARY attribute to complement the CAPTION:
Symbols and Greek Letters in HTML 4.0
Character
Entity
Decimal
Hex
Latin small f with hook
ƒ
ƒ
ƒ
...
The deprecated ALIGN attribute of CAPTION specifies the alignment of the
caption relative to the table. Possible values are top (the default), bottom,
left, and right.
═══ 1.5.17. CENTER - Centered block ═══
CENTER - Centered Block
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements, block-level elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The CENTER element defines a block whose contents are centered horizontally
on visual browsers. is a shorthand for < DIV ALIGN=center>, though
CENTER is slightly better supported among browsers. Both methods of centering
are deprecated in favor of style sheets.
CENTER is still useful for centering tables since many browsers lack support
for as well as the method of centering tables with
Cascading Style Sheets (setting margin-left and margin-right to auto). An
example follows:
Name
Age
Country
Liam Quinn
20
Canada
Note that CENTER only centers the table as a whole, not the contents of each
table cell. The preceding example uses the ALIGN attribute of TR to center
the contents of each cell. The text-align property of Cascading Style Sheets
provides greater flexibility in suggesting horizontal alignment.
═══ 1.5.18. CITE - Citation ═══
CITE - Citation
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The CITE element is used to markup citations, such as titles of magazines or
newspapers, ship names, references to other sources, and quotation
attributions. Visual browsers typically render CITE as italic text, but
authors can suggest a rendering using style sheets. Since CITE is a
structural element, it carries meaning, making it preferable to font style
elements such as I when marking up citations.
Example:
The Toronto Star gave its review of the movie
Titanic yesterday.
═══ 1.5.19. CODE - Computer code ═══
CODE - Computer Code
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The CODE element denotes computer code. Visual browsers typically render CODE
as monospaced text, but authors can suggest a rendering using style sheets.
Since CODE is a structural element, it carries meaning, making it preferable
to font style elements such as TT when marking up computer code.
Since spacing is often important when presenting computer code, the PRE
element can be useful as a container for CODE elements. When used within
other containers, a CODE element has multiple spaces collapsed. The following
example uses CODE within PRE:
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
═══ 1.5.20. COL - Table column ═══
COL - Table Column
Syntax
Character Entity
Decimal
Hex
Rendering in Your Browser
Entity
Decimal
Hex
non-breaking space
 
 
...
COL also takes a number of presentational attributes, many of which cannot be
completely replaced by style sheets. Since few browsers support COL, authors
may wish to specify these attributes on the TD or TH elements instead.
The WIDTH attribute specifies a width for each column spanned by COL. The
value must be a number in pixels, a percentage of the table width, or a
relative length expressed as i* where i is an integer. A column with
WIDTH="3*" will be allotted three times the width of a column with WIDTH="1*".
The value 0* is equivalent to the minimum width necessary for the column's
contents.
The ALIGN attribute specifies the horizontal alignment for each cell in the
spanned columns. Possible values are left, center, right, justify, and char.
ALIGN=char aligns a cell's contents on the character given in the CHAR
attribute. The default value for the CHAR attribute is the decimal point of
the current language--a period in English. The CHAROFF attribute specifies
the offset to the first occurrence of the alignment character. The attribute's
value is a number in pixels or a percentage of the cell's width; CHAROFF="50%"
centers the alignment character horizontally in a cell.
The VALIGN attribute specifies the vertical position of a cell's contents.
Possible values are:
o top, which positions data at the top of the cell;
o middle, the default value, which centers the cell data vertically;
o bottom, which positions data at the bottom of the cell;
o baseline, which specifies that the first line of each cell in the row with
ALIGN=baseline should occur on a common baseline.
═══ 1.5.21. COLGROUP - Table column group ═══
COLGROUP - Table Column Group
Syntax
...
Attribute Specifications
o SPAN= Number (number of columns in group)
o WIDTH= MultiLength (width of each column)
o ALIGN=[ left | center | right | justify | char ] (horizontal alignment of
cells in group)
o CHAR= Character (alignment character for cells)
o CHAROFF= Length (alignment character offset)
o VALIGN=[ top | middle | bottom | baseline ] (vertical alignment of cells
in group)
o common attributes
Contents
Zero or more COL elements
Contained in
TABLE
The COLGROUP element defines a column group in a table. If used, COLGROUP
must be after the optional CAPTION and before the optional THEAD in the
TABLE. The structural divisions defined by COLGROUP allow authors to easily
suggest a presentation for groups of columns through style sheets.
COLGROUP's SPAN attribute defines the number of columns in the group; the
default value is 1. A number of other attributes are permitted on COLGROUP,
and these are shared among the cells of the group. COLGROUP may contain COL
elements that define attributes for the cells of individual columns, overriding
attributes defined for the column group. The SPAN attribute should not be
used if the COLGROUP contains any COL elements.
The next example features three column groups to structurally divide the table
into three parts. The first part is a single column that gives the description
of a character. The second part consists of three columns giving different
ways of representing the character in HTML. The third part consists of three
columns with renderings of the character in the user's browser.
Character
Entity
Decimal Hex
Rendering in Your Browser
Entity
Decimal
Hex
non-breaking space
 
 
...
In place of the tag in the preceding example, a COLGROUP
with three COL elements could have been used:
Here we have used the CLASS attribute to distinguish the individual columns
of the group, allowing us to easily suggest different presentations for the
columns through style sheets.
COLGROUP also takes a number of presentational attributes, many of which
cannot be completely replaced by style sheets. Since few browsers support
COLGROUP, authors may wish to specify these attributes on the TD or TH
elements instead.
The WIDTH attribute specifies a width for each column in the group. The value
must be a number in pixels, a percentage of the table width, or a relative
length expressed as i* where i is an integer. A column with WIDTH="3*" will
be allotted three times the width of a column with WIDTH="1*". The value 0*
is equivalent to the minimum width necessary for the column's contents.
The ALIGN attribute specifies the horizontal alignment for each cell in the
column group. Possible values are left, center, right, justify, and char.
ALIGN=char aligns a cell's contents on the character given in the CHAR
attribute. The default value for the CHAR attribute is the decimal point of
the current language--a period in English. The CHAROFF attribute specifies
the offset to the first occurrence of the alignment character. The attribute's
value is a number in pixels or a percentage of the cell's width; CHAROFF="50%"
centers the alignment character horizontally in a cell.
The VALIGN attribute specifies the vertical position of a cell's contents.
Possible values are:
o top, which positions data at the top of the cell;
o middle, the default value, which centers the cell data vertically;
o bottom, which positions data at the bottom of the cell;
o baseline, which specifies that the first line of each cell in the row with
ALIGN=baseline should occur on a common baseline.
═══ 1.5.22. DD - Definition description ═══
DD - Definition Description
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements, block-level elements
Contained in
DL
The DD element provides the definition of a term in a definition list. The
closing tag for DD is optional, but its use prevents common browser bugs with
style sheets.
DD may contain block-level elements such as P, H2, TABLE, and DL. This
allows definition lists to be nested, as in the following example:
- Spanning tree
-
A spanning tree of a graph is a tree
that contains all the vertices of the graph. There are two
main types of spanning trees:
- BFS spanning tree
-
A spanning tree formed by a breadth-first search on the graph.
- DFS spanning tree
-
A spanning tree formed by a depth-first search on the graph.
- Tree
-
A tree is connected, undirected graph without cycles.
A DD element should generally be preceded by a DT element that gives the
term defined by the DD. A single definition term may have multiple definitions
associated with it, and a single definition may have multiple terms.
═══ 1.5.23. DEL - Deleted text ═══
DEL - Deleted Text
Syntax
...
Attribute Specifications
o CITE= URI (reason for deletion)
o DATETIME= Datetime (date and time of deletion)
o common attributes
Contents
Inline elements, block-level elements
Contained in
Inline elements, block-level elements
The DEL element contains content that has been deleted. This element is
useful in marking changes from one version of a document to the next. Through
style sheets, authors can suggest an appropriate rendering, such as not
displaying the deleted content or rendering the text with a strike-through
style.
DEL may be used as either a block-level element or an inline element. If
used as an inline element (e.g., within a P), then DEL may not contain any
block-level elements.
The optional CITE attribute of DEL gives a URI with information on why the
content was deleted. A brief explanation for the deletion can be given with
the TITLE attribute, which may be rendered as a "tooltip" by some browsers.
The optional DATETIME attribute specifies the date and time of the deletion.
The value is case-sensitive and of the form YYYY-MM-DDThh:mm:ssTZD. See the
values section for a full explanation of this format.
An example follows:
The XMP element contains preformatted text in which markup
other than an end tag is treated as literal
text.
Since DEL is poorly supported among browsers, authors may wish to use a font
style element such as STRIKE ( deprecated in HTML 4.0) to attempt to convey
the meaning of DEL to non-supporting visual browsers. The previous example
could also be marked up as follows:
The XMP element is used for preformatted text in
which markup other than an end tag is treated as literal
text.
═══ 1.5.24. DFN - Defined term ═══
DFN - Defined Term
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The DFN element denotes the defining instance of a term. Visual browsers
typically render DFN as italic text, but authors can suggest a rendering using
style sheets. Since DFN is a structural element, it carries meaning, making
it preferable to font style elements such as I when marking up the defining
instance of a term.
Netscape Navigator does not support the DFN element. In most cases, the lack
of support is not a significant problem; concerned authors could nest the DFN
element within an I element or another font style element.
═══ 1.5.25. DIR - Directory List ═══
DIR
Syntax
...
Attribute Specifications
o COMPACT (compact display)
o common attributes
Contents
One or more LI elements that cannot contain block-level elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The DIR element defines a directory list. The element contains one or more
LI elements that define the actual items of the list. The LI elements must
not contain block-level elements, which prevents DIRs from being nested.
The COMPACT attribute suggests that visual browsers render the list compactly,
perhaps with reduced spacing between items. This attribute is not well
supported among browsers.
DIR is deprecated in HTML 4.0 in favor of UL.
═══ 1.5.26. DIV - Generic block-level container ═══
DIV - Generic Block-level Container
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements, block-level elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The DIV element defines a generic block-level container, allowing authors to
provide style or language information to blocks of content. The element may
contain any inline or block-level element, including another DIV.
The DIV element is most useful in combination with the CLASS, ID, or LANG
attributes. For example, a navigation bar could be contained within a DIV
marked as CLASS=navbar, allowing the author to use style sheets to easily
change the background of all navigation bars on a site, or to eliminate
navigation bars when printing.
The deprecated ALIGN attribute suggests the horizontal alignment for the
content of the division on visual browsers. Possible values are left, right,
center, and justify. is a slightly better-supported alias for , though both methods of centering are deprecated in favor of
style sheets, which provide greater flexibility in suggesting alignment.
SPAN is a text-level equivalent of DIV for use within paragraphs and inline
elements.
═══ 1.5.27. DL - Definition list ═══
DL - Definition List
Syntax
...
Attribute Specifications
o COMPACT (compact display)
o common attributes
Contents
One or more DT or DD elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The DL element defines a definition list. An entry in the list is created
using the DT element for the term being defined and the DD element for the
definition of the term.
A definition list can have multiple terms for a given definition as well as
multiple definitions for a given term. Authors can also give a term without a
corresponding definition, and vice versa, but such a structure rarely makes
sense.
An example follows:
- Block-level elements
-
In HTML, block-level elements may generally contain
inline elements and other block-level elements. They are
usually formatted differently than inline elements,
typically on a new line in visual browsers.
- Inline elements
- Text-level elements
-
Inline (or text-level) elements generally only contain
character data and other inline elements.
The DL element can be adapted for use with structures that are not strict
terms and definitions, a practice that is justified when other HTML elements
cannot adequately describe a structure. Some examples follow:
Community Calendar
- March 8
-
The Symphony Orchestra presents A Rising Star
at the Anderson Center. Call 555-1234 for details.
- March 10
-
Bereaved Families Support Night, 7:00 to 9:00 at
523 Main St.
- Brutus
-
I kiss thy hand, but not in flattery, Caesar;
Desiring thee that Publius Cimber may
Have an immediate freedom of repeal.
- Caesar
-
What, Brutus!
- Cassius
-
Pardon, Caesar; Caesar, pardon:
As low as to thy foot doth Cassius fall,
To beg enfranchisement for Publius Cimber.
Note the use of the CLASS attribute in the preceding examples. This allows
the author to easily suggest, through style sheets, a distinguishing
presentation for different kinds of definition lists.
In addition to the common attributes shared by most elements, DL takes a
COMPACT attribute. This attribute, deprecated in HTML 4.0 and poorly
supported among browsers, suggests that visual browsers render the list
compactly, perhaps with reduced spacing between items.
═══ 1.5.28. DT - Definition term ═══
DT - Definition Term
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
DL
The DT element defines a term in a definition list. The closing tag for DT
is optional, but its use prevents common browser bugs with style sheets. Note
that DT cannot contain block-level elements such as P and H2.
A DT element should generally be followed by a DD element that provides the
definition for the term given by the DT. A single definition term may have
multiple definitions associated with it, and a single definition may have
multiple terms.
═══ 1.5.29. EM - Emphasis ═══
EM - Emphasis
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The EM element gives emphasis to its contents. Visual browsers typically
render EM as italic text, but authors can suggest a rendering using style
sheets. Since EM is a structural element, it carries meaning, making it
preferable to font style elements such as I when emphasis is the intended
meaning.
For strong emphasis, use the STRONG element.
═══ 1.5.30. FIELDSET - Form control group ═══
FIELDSET - Form Control Group
Syntax
Attribute Specifications
o common attributes
Contents
A LEGEND element followed by zero or more block-level elements and
inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, CENTER, DD, DEL, DIV, FIELDSET, FORM,
IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The FIELDSET element defines a form control group. By grouping related form
controls, authors can divide a form into smaller, more manageable parts,
improving the usability disaster that can strike when confronting users with
too many form controls. The grouping provided by FIELDSET also helps the
accessibility of forms to those using aural browsers by allowing these users to
more easily orient themselves when filling in a large form.
While FIELDSET is not widely supported by current browsers, it can be used
safely by explicitly closing any preceding P element with or by
including an empty P prior to the FIELDSET. This causes non-supporting
browsers to infer the start of a block-level element even though they ignore
the block-level FIELDSET element.
The content of a FIELDSET element must begin with a LEGEND to provide a
caption for the group of controls. Following the LEGEND, FIELDSET may contain
any inline or block-level element, including another FIELDSET.
An example follows:
═══ 1.5.31. FONT - Font change ═══
FONT - Font Change
Syntax
...
Attribute Specifications
o SIZE= CDATA (font size adjustment)
o COLOR= Color (font color adjustment)
o FACE= CDATA (font face adjustment)
o core attributes
o internationalization attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements except PRE
The FONT element, deprecated in HTML 4.0 in favor of style sheets, allows
authors to suggest rudimentary font changes. Use of the FONT element brings
numerous usability and accessibility problems, as discussed in the article
What's Wrong With FONT?
The least harmful use of the FONT element is in suggesting relative changes in
font size with or . These tags increment or
decrement the font size relative to the size specified in the BASEFONT
element, or relative to a base size of 3 if no BASEFONT element is used.
Sizes are based on a seven-point scale (1..7) that is browser dependent.
While authors can specify SIZE values such as -2 and +3, as well as absolute
values such as 1, these kinds of changes are strongly discouraged due to the
sensitivity some users have to different font sizes. While a value like -2
may look right to you with your eyesight and user settings, it could easily be
unreadable to a user with different eyesight and user settings.
The COLOR attribute suggests a text color. While most browsers allow users to
override author color changes, the widely used Netscape Navigator 2.x, 3.x, and
4.x do not override colors specified with FONT. This makes the COLOR
attribute very dangerous from an accessibility point of view.
Authors often use the COLOR attribute as a form of emphasis or to indicate a
heading. In these cases, use of structural HTML (e.g., STRONG, H1) along
with a style sheet provides a more flexible, accessible document.
The FACE attribute gives a comma-separated list of font faces in which to
display text. The fonts are listed in order of preference, so that if the
browser does not have the first font listed, it will try the second, then the
third, and so on.
The FONT element is an inline element, meaning that it cannot contain
block-level elements such as P and TABLE. Again, style sheets provide
much more flexibility in suggesting font styles.
═══ 1.5.32. FORM - Interactive form ═══
FORM - Interactive Form
Syntax
Attribute Specifications
o ACTION= URI (form handler)
o METHOD=[ get | post ] (HTTP method for submitting form)
o ENCTYPE= ContentType (content type to submit form as)
o ACCEPT-CHARSET= Charsets (supported character encodings)
o TARGET= FrameTarget (frame to render form result in)
o ONSUBMIT= Script (form was submitted)
o ONRESET= Script (form was reset)
o common attributes
Contents
o In HTML 4.0 Strict, one or more SCRIPT or block-level elements except
FORM
o In HTML 4.0 Transitional, inline elements or block-level elements except
FORM
Contained in
APPLET, BLOCKQUOTE, BODY, CENTER, DD, DEL, DIV, FIELDSET, IFRAME,
INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The FORM element defines an interactive form. The element should contain form
controls-- INPUT, SELECT, TEXTAREA, and BUTTON--through which the user
interacts.
When the user submits the form, through an INPUT or BUTTON element with
TYPE=submit, the form values are submitted to the URI given in FORM's required
ACTION attribute. ACTION usually points to a CGI script or Java servlet
that handles the form submission.
A mailto URI (e.g., mailto:liam@htmlhelp.com) is also allowed as an ACTION,
but this is not supported by all browsers. Non-supporting browsers such as
Microsoft Internet Explorer 3.x typically will open a blank e-mail message when
the user submits a mailto form. Even on supporting browsers, mailto forms are
troublesome in that they fail to provide feedback to the user after the form
submission.
Free CGI scripts exist for handling forms; some are even remotely hosted for
authors whose providers refuse to allow CGI scripts to be run locally.
How the form input is sent to the server depends on the METHOD and ENCTYPE
attributes. When the METHOD is get (the default), the form input is
submitted as an HTTP GET request with ?form_data appended to the URI
specified in the ACTION attribute.
Using the get method allows the form submission to be contained completely in
a URL. This can be advantageous in that it permits bookmarking in current
browsers, but it also prevents form data from containing non-ASCII characters
such as "щ" and "й". As well, the amount of form data that can be handled by
the get method is limited by the maximum length of the URL that the server
and browser can process. To be safe, any form whose input might contain
non-ASCII characters or more than 100 characters should use METHOD=post.
With a METHOD value of post, the form input is submitted as an HTTP POST
request with the form data sent in the body of the request. Most current
browsers are unable to bookmark POST requests, but POST does not entail the
character encoding and length restrictions imposed by GET.
The ENCTYPE attribute specifies the content type used in submitting the form,
and defaults to application/x-www-form-urlencoded. This content type results
in name/value pairs sent to the server as name1=value1&name2=value2... with
space characters replaced by "+" and reserved characters (like "#") replaced by
"%HH" where HH is the ASCII code of the character in hexadecimal. Line
breaks are encoded as "%0D%0A"--a carriage return followed by a line feed.
Authors should generally only use a different ENCTYPE when the form includes a
TYPE=file INPUT element, in which case the ENCTYPE should be
multipart/form-data and the METHOD must be post. The format of
multipart/form-data requests is given in RFC 1867.
Tools such as cg-eye allow authors to easily create and view a request,
simulating the submission of a form. However, authors often do not need to
concern themselves with the exact format of the submission; CGI libraries
including CGI.pm transparently handle get and post submissions sent as
application/x-www-form-urlencoded or multipart/form-data.
The ACCEPT-CHARSET attribute specifies a list of character encodings that are
accepted by the form handler. The value consists of a list of "charsets"
separated by commas and/or spaces. The default value is UNKNOWN and is
usually considered to be the character encoding used to transmit the document
containing the FORM.
The TARGET attribute is used with frames to specify in which frame the form
response should be rendered. If no frame with such a name exists, the response
is rendered in a new window unless overridden by the user. Special frame names
begin with an underscore:
o _blank renders the response in a new, unnamed window
o _self renders the response in the current frame (useful for overriding a
BASE TARGET)
o _parent renders the response in the immediate FRAMESET parent
o _top renders the response in the full, unframed window
The FORM element also takes a number of attributes to specify client-side
scripting actions for various events. In addition to the core events common
to most elements, INPUT accepts the following event attributes:
o ONSUBMIT, when the form is submitted;
o ONRESET, when the form is reset.
═══ 1.5.33. FRAME - Frame ═══
FRAME - Frame
Syntax
Attribute Specifications
o NAME= CDATA (name of frame)
o SRC= URI (content of frame)
o LONGDESC= URI (long description of frame)
o FRAMEBORDER=[ 1 | 0 ] (frame border)
o MARGINWIDTH= Pixels (margin width)
o MARGINHEIGHT= Pixels (margin height)
o NORESIZE (disallow frame resizing)
o SCROLLING=[ yes | no | auto ] (ability to scroll)
o core attributes
Contents
Empty
Contained in
FRAMESET
The FRAME element defines a frame--a rectangular subspace within a Frameset
document. Each FRAME must be contained within a FRAMESET that defines the
dimensions of the frame.
The SRC attribute provides the URI of the frame's content, which is typically
an HTML document. If the frame's content is an image, video, or similar
object, and if the object cannot be described adequately using the TITLE
attribute of FRAME, then authors should use the LONGDESC attribute to provide
the URI of a full HTML description of the object.
For better accessibility to disabled users and better indexing with search
engines, authors should not use an image or similar object as the content of a
frame. Rather, the object should be embedded within an HTML document to allow
the indexing of keywords and easier provision of alternate content.
The NAME attribute gives a name to the frame for use with the TARGET
attribute of the A, AREA, BASE, FORM, and LINK elements. The NAME
attribute value must begin with a character in the range A-Z or a-z.
The NAME should be human-readable and based on the content of the frame since
non-windows browsers may use the NAME as a title for presenting a list of
frames to the user. For example, NAME=left would be inappropriate since it
says nothing about the content while NAME=nav would be inappropriate since it
is not very human-readable. More suitable would be NAME=Content and
NAME=Navigation. The TITLE attribute can also be used to provide a slightly
longer title for the frame, though this is not widely supported by current
browsers.
An example follows:
The FRAME element also accepts a number of attributes to specify the
presentation on visual browsers. Style sheets provide a more flexible method
of defining the presentation of frames, but the element's presentational
attributes are more widely supported.
The FRAMEBORDER attribute specifies whether or not the frame has a visible
border. The default value, 1, tells the browser to draw a border between the
frame and all adjoining frames. The value 0 indicates that no border should
be drawn, though borders from other frames will override this.
To fully remove the border, some browsers also require the use of other,
non-standard attributes. See How do I remove the border around frames? for
more details.
Note that removing the border of a frame takes away the user's ability to
resize the frame on most browsers.
The MARGINWIDTH and MARGINHEIGHT attributes define the number of pixels to
use as the left/right margins and top/bottom margins, respectively, within the
frame. The value must be greater than one pixel.
The boolean NORESIZE attribute prevents the user from resizing the frame.
This attribute should never be used in a user-friendly Web site.
The SCROLLING attribute specifies whether scrollbars are provided for the
frame. The default value, auto, generates scrollbars only when necessary. The
value yes gives scrollbars at all times, and the value no suppresses
scrollbars--even when they are needed to see all the content. The value no
should never be used.
═══ 1.5.34. FRAMESET - Frameset ═══
FRAMESET - Frameset
Syntax
Attribute Specifications
o ROWS= MultiLengths (row lengths)
o COLS= MultiLengths (column lengths)
o ONLOAD= Script (all frames have been loaded)
o ONUNLOAD= Script (all frames have been removed)
o core attributes
Contents
One or more FRAMESET and FRAME elements, as well as an optional
NOFRAMES
Contained in
HTML
The FRAMESET element is a frame container for dividing a window into
rectangular subspaces called frames. In a Frameset document, the outermost
FRAMESET element takes the place of BODY and immediately follows the HEAD.
The FRAMESET element contains one or more FRAMESET or FRAME elements, along
with an optional NOFRAMES element to provide alternate content for browsers
that do not support frames or have frames disabled. A meaningful NOFRAMES
element should always be provided and should at the very least contain links to
the main frame or frames.
The ROWS and COLS attributes define the dimensions of each frame in the set.
Each attribute takes a comma-separated list of lengths, specified in pixels, as
a percentage, or as a relative length. A relative length is expressed as i*
where i is an integer. For example, a frameset defined with ROWS="3*,*" (*
is equivalent to 1*) will have its first row allotted three times the height of
the second row.
The values specified for the ROWS attribute give the height of each row, from
top to bottom. The COLS attribute gives the width of each column from left to
right. If ROWS or COLS is omitted, the implied value for the attribute is
100%. If both attributes are specified, a grid is defined and filled
left-to-right then top-to-bottom.
The following example sets up a grid with two rows and three columns:
The next example features nested FRAMESET elements to define two frames in the
first row and one frame in the second row:
When pixel lengths are used, they should always be combined with a relative
length to handle various window sizes. Pixel lengths should only be used when
the frame consists primarily of images or other objects with a fixed size in
pixels. Due to their ability to adapt to different window sizes, percentages
and relative lengths are generally preferred.
The FRAMESET element also accepts ONLOAD and ONUNLOAD attributes to specify
client-side scripting actions to perform when the frames have all been loaded
or removed.
═══ 1.5.35. H1 - Level-one heading ═══
H1 - Level-one Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H1 element defines a level-one heading. A document generally should have
exactly one H1 element to mark the most important heading.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H1 in a large, bold font. Authors can suggest
a presentation for H1 through style sheets. The following CSS ruleset
suggests a presentation for all H1 elements:
h1 { color: #c33;
background: transparent;
font-weight: bold;
text-align: center
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H1 is typically used as the main
heading for a document.
═══ 1.5.36. H2 - Level-two heading ═══
H2 - Level-two Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H2 element defines a level-two heading. This heading is more important
than an H3 but less important than an H1.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H2 in a large, bold font. Authors can suggest
a presentation for H2 through style sheets. The following CSS ruleset
suggests a presentation for all H2 elements:
h2 {
color: #00008b;
background: transparent;
font-weight: bold;
margin-left: 2%;
margin-right: 2%
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H2 is typically used within a
section headed by an H1.
═══ 1.5.37. H3 - Level-three heading ═══
H3 - Level-three Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H3 element defines a level-three heading. This heading is more important
than an H4 but less important than an H2.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H3 in a bold font. Authors can suggest a
presentation for H3 through style sheets. The following CSS ruleset
suggests a presentation for all H3 elements:
h3 {
color: #006400;
background: transparent;
margin-left: 4%;
margin-right: 4%;
font-weight: bold
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H3 is typically used within a
section headed by an H2.
═══ 1.5.38. H4 - Level-four heading ═══
H4 - Level-four Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H4 element defines a level-four heading. This heading is more important
than an H5 but less important than an H3.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H4 in a bold font. Authors can suggest a
presentation for H4 through style sheets. The following CSS ruleset
suggests a presentation for all H4 elements:
h4 {
margin-left: 6%;
margin-right: 6%;
font-weight: bold
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H4 is typically used within a
section headed by an H3.
═══ 1.5.39. H5 - Level-five heading ═══
H5 - Level-five Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H5 element defines a level-five heading. This heading is more important
than an H6 but less important than an H4.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H5 in a small, bold font. Authors can suggest
a presentation for H5 through style sheets. The following CSS ruleset
suggests a presentation for all H5 elements:
h5 {
margin-left: 6%;
margin-right: 6%;
font-size: 110%;
font-weight: bold
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H5 is typically used within a
section headed by an H4.
═══ 1.5.40. H6 - Level-six heading ═══
H6 - Level-six Heading
Syntax
...
Attribute Specifications
o ALIGN=[ left | center | right | justify ] (horizontal alignment)
o common attributes
Contents
Inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DEL, DD, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The H6 element defines a level-six heading. This heading is less important
than an H5.
The deprecated ALIGN attribute suggests the horizontal alignment for the
heading on visual browsers. Possible values are left, right, center, and
justify. Style sheets provide greater flexibility in suggesting alignment.
Visual browsers typically render H6 in a small, bold font. Authors can suggest
a presentation for H6 through style sheets. The following CSS ruleset
suggests a presentation for all H6 elements:
h6 {
margin-left: 6%;
margin-right: 6%;
font-size: 105%;
font-weight: bold
}
Authors should not choose a heading level based on the font size commonly used
by visual browsers. The heading level should be chosen based on the heading's
importance and placement in the document. An H6 is typically used within a
section headed by an H5.
═══ 1.5.41. HEAD - Document head ═══
HEAD - Document Head
Syntax
...
Attribute Specifications
o PROFILE= URI (dictionary of meta info)
o internationalization attributes
Contents
Exactly one TITLE element, optional BASE and ISINDEX elements, and
zero or more SCRIPT, STYLE, META, LINK, or OBJECT elements
Contained in
HTML
The HEAD element contains header information about the document, such as its
title, keywords, description, and style sheet. HEAD is required in all
documents, but its start and end tags are always optional. The HEAD element
is followed by the BODY in HTML 4.0 Strict and Transitional documents; in
HTML 4.0 Frameset documents, the HEAD is followed by a FRAMESET element.
Content in the HEAD is generally not rendered, with the exception of the
required TITLE element. If the end tag is omitted, the first BODY
or FRAMESET element infers the end of the HEAD.
The optional PROFILE attribute of HEAD gives the location of a metadata
profile. A profile defines properties that may be used by META and LINK
elements within the HEAD. There is no prescribed format for profiles.
Work is currently underway on improving the use of metadata on the Web. See the
W3C's Metadata and Resource Description area for the latest information.
═══ 1.5.42. HR - Horizontal rule ═══
HR - Horizontal Rule
Syntax
Attribute Specifications
o ALIGN=[ left | center | right ] (horizontal alignment)
o NOSHADE (solid line)
o SIZE= Pixels (line height)
o WIDTH= Length (line width)
o core attributes
o common events
Contents
Empty
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The HR element defines a horizontal rule for visual browsers. While this
element is inherently presentational, it can be used structurally as a section
divider. However, for greater flexibility the HR element can be replaced with
the border-bottom or border-top properties of Cascading Style Sheets. For
example, the following style rule would suggest a horizontal line above all
DIV elements with CLASS=navbar:
div.navbar { border-top: solid medium navy }
HR's deprecated ALIGN attribute suggests the horizontal alignment of the
line. Possible values are left, right, and center. The deprecated WIDTH
attribute specifies the width of the line as a percentage or a number of
pixels. If a width is specified, percentages are generally preferred since
they adjust to varying window sizes. The width property of Cascading Style
Sheets provides greater flexibility in suggesting the width of horizontal
rules.
The boolean NOSHADE attribute suggests that the rule be rendered as a solid
line rather than the groove style commonly used. The SIZE attribute suggests
the height of the line in pixels. These attributes are both deprecated in
favor of style sheets.
═══ 1.5.43. HTML - HTML document ═══
HTML - HTML Document
Syntax
...
Attribute Specifications
o VERSION= CDATA (HTML version)
o internationalization attributes
Contents
o In HTML 4.0 Strict and Transitional: HEAD followed by BODY
o In HTML 4.0 Frameset: HEAD followed by FRAMESET
Contained in
Not applicable--HTML is a top-level element
The HTML element contains the HTML document, made up of the HEAD followed by
the BODY, except in Frameset documents where the FRAMESET element replaces
the BODY. The start and end tags of the HTML element are both optional.
The LANG attribute is typically set on the HTML element to specify the base
language of the document. The language should be specified according to RFC
1766; examples include en for English, en-US for American English, and ja
for Japanese.
The deprecated VERSION attribute specifies the Document Type Definition (DTD)
that describes the document. This attribute should not be used since the
DOCTYPE declaration makes it redundant.
═══ 1.5.43.1. DOCTYPE - Document Type Declaration ═══
DOCTYPE - Document Type Declaration
Each HTML document must begin with a document type declaration that declares
which version of HTML the document adheres to. HTML 4.0 comes in three flavors,
each with a different DOCTYPE:
HTML 4.0 Strict
HTML 4.0 Strict is a trimmed down version of HTML 4.0 that
emphasizes structure over presentation. Deprecated elements and
attributes (including most presentational attributes), frames, and
link targets are not allowed in HTML 4.0 Strict . By writing to HTML
4.0 Strict authors can achieve accessible, structurally rich
documents that easily adapt to style sheets and different browsing
situations. However, since many browsers lack full support for style
sheets, HTML 4.0 Strict documents may look bland on common visual
browsers such as Netscape Navigator 3.x.
The document type declaration for HTML 4.0 Strict is
HTML 4.0 Transitional
HTML 4.0 Transitional includes all elements and attributes of HTML
4.0 Strict but adds presentational attributes, deprecated elements,
and link targets. HTML 4.0 Transitional recognizes the relatively
poor browser support for style sheets, allowing many HTML
presentation features to be used as a transition towards HTML 4.0
Strict.
The document type declaration for HTML 4.0 Transitional is
HTML 4.0 Frameset
HTML 4.0 Frameset is a variant of HTML 4.0 Transitional for documents
that use frames. The FRAMESET element replaces the BODY in a Frameset
document.
The document type declaration for HTML 4.0 Frameset is
═══ 1.5.44. I - Italic text ═══
I - Italic Text
Syntax
...
Attribute Specifications
o common attributes
Contents
Inline elements
Contained in
Inline elements, block-level elements
The I element suggests that text be rendered as italic text. In most cases, use
of a phrase elemens such as EM, DFN, VAR, or CITE is more appropriate since
these elements express the meaning of the text more clearly.
The I element is a suitable choice for marking a structure for which no phrase
elemens exists. For example, foreign phrases and taxonomic names have no
structural element in HTML 4.0, but italic text is often an appropriate visual
rendering:
Chacun son go√t !
Some people prefer dogs--
Canis familiaris
--while others are eternal lovers of cats--
Felis cattus.
Note the use of the CLASS and LANG attributes to add structural significance to
the I elements. This allows greater flexibility when applying style sheets to
different kinds of italic text.
═══ 1.5.45. IFRAME - Inline frame ═══
IFRAME - Inline Frame
Syntax
Attribute Specifications
o SRC= URI (URI of frame content)
o NAME= CDATA (name of frame)
o LONGDESC= URI (link to long description)
o WIDTH= Length (frame width)
o HEIGHT= Length (frame height)
o ALIGN=[ top | middle | bottom | left | right ] (frame alignment)
o FRAMEBORDER=[ 1 | 0 ] (frame border)
o MARGINWIDTH= Pixels (margin width)
o MARGINHEIGHT= Pixels (margin height)
o SCROLLING=[ yes | no | auto ] (ability to scroll)
o core attributes
Contents
Inline elements, block-level elements
Contained in
Inline elements, block-level elements
The IFRAME element defines an inline frame for the inclusion of external
objects including other HTML documents. IFRAME provides a subset of the
functionality of OBJECT; the only advantage to IFRAME is that an inline frame
can act as a target for other links. OBJECT is more widely supported than
IFRAME, and, unlike IFRAME, OBJECT is included in HTML 4.0 Strict.
IFRAME's SRC attribute provides the location of the frame content--typically
an HTML document. The optional NAME attribute specifies the name of the inline
frame, allowing links to target the frame.
The content of the IFRAME element is used as an alternative for browsers that
are not configured to show or do not support inline frames. The content may
consist of inline or block-level elements, though any block-level elements
must be allowed inside the containing element of IFRAME. For example, an IFRAME
within an H1 cannot contain an H2, but an IFRAME within a DIV can contain
any block-level elements.
The LONGDESC attribute gives the URI of a long description of the frame's
contents. This is particularly useful for full descriptions of embedded
objects. Note that LONGDESC describes the frame content while the content of
the IFRAME element acts as a replacement when the external resource cannot be
inlined.
An example follows:
The WIDTH and HEIGHT attributes specify the dimensions of the inline frame in
pixels or as a percentage of the available space. The FRAMEBORDER attribute
specifies whether or not a border should be drawn. The default value of 1
results in a border while a value of 0 suppresses the border. Style sheets
allow greater flexibility in suggesting the border presentation.
The ALIGN attribute specifies the alignment of the inline frame. The values
top, middle, and bottom specify the frame's position with respect to
surrounding content on its left and right.
ALIGN=middle aligns the center of the frame with the current baseline. To
center the frame horizontally on the page, place the frame in a centered block,
e.g.,
The other ALIGN values, left and right, specify a floating frame; the frame
is placed at the left or right margin and content flows around it. To place
content below the frame, use
as appropriate.
The vertical-align and float properties of Cascading Style Sheets provide
more flexible methods of aligning inline frames.
The MARGINWIDTH and MARGINHEIGHT attributes define the number of pixels to
use as the left/right margins and top/bottom margins, respectively, within the
inline frame. The value must be greater than one pixel.
The SCROLLING attribute specifies whether scrollbars are provided for the
inline frame. The default value, auto, generates scrollbars only when
necessary. The value yes gives scrollbars at all times, and the value no
suppresses scrollbars--even when they are needed to see all the content. The
value no should never be used.
═══ 1.5.46. IMG - Inline image ═══
IMG - Inline Image
Syntax
![]()
Attribute Specifications
o SRC= URI (location of image)
o ALT= Text (alternate text)
o LONGDESC= URI (link to long description)
o WIDTH= Length (image width)
o HEIGHT= Length (image height)
o USEMAP= URI (client-side image map)
o ISMAP (server-side image map)
o ALIGN=top|middle|bottom|left|right (image alignment)
o BORDER= Length (link border width)
o HSPACE= Pixels (horizontal gutter)
o VSPACE= Pixels (vertical gutter)
o common attributes
Contents
Empty
Contained in
Inline elements, block-level elements except PRE
The IMG element specifies an inline image. The required SRC attribute
specifies the location of the image. The image can be any format, though
browsers generally only support GIF and JPEG images. Support for the PNG
image format is growing slowly.
The required ALT attribute provides alternate text for those not loading
images. Effective ALT text should generally give the function of the image
rather than a description of the image. For example, ALT="Welcome to XYZ
Corp." would be more appropriate than ALT="XYZ Corp. Logo" for a company's
logo on its welcome page. Good ALT text is crucial to the document's
accessibility for the significant portion of users who do not load images; see
Use of ALT texts in IMGs for a thorough discussion.
The LONGDESC attribute gives the location of a long description of the image.
This attribute should be used to provide a long description of an image where
this would be useful. For example, a painting, graph, or corporate logo could
be given a description so that blind and other text-only users can develop a
mental picture of the image.
The WIDTH and HEIGHT attributes are most useful when they specify the exact
dimensions of the image in pixels. This allows image-loading browsers to
reserve the proper amount of space for the image and continue to render the
rest of the document, thus giving the appearance of a faster-loading page.
Unfortunately, many graphical browsers will use these dimensions when not
loading images, which can cause the ALT text to be cut off if the image is
small or the ALT text is large. In such cases, authors may wish to leave off
the WIDTH and HEIGHT attributes, depending on the importance of the ALT text
and the placement of the image on the page (an image towards the end of the
document without WIDTH and HEIGHT attributes will generally not noticeably
slow the rendering of the page).
Authors can also specify different dimensions for the WIDTH and HEIGHT
attributes, in which case browsers should scale the image. Percentages,
relative to the horizontal or vertical space available (not relative to the
image's natural size) can also be specified, though these are not as widely
supported as pixel lengths. Since browsers typically do a poor job of scaling
images, authors should avoid using WIDTH and HEIGHT for this purpose as much
as possible.
The ALIGN attribute, deprecated in HTML 4.0, specifies the alignment of the
image. The values top, middle, and bottom specify the image's position with
respect to surrounding content on its left and right.
ALIGN=middle aligns the center of the image with the current baseline. To
center the image horizontally on the page, place the image in a centered block,
e.g.,
The other ALIGN values, left and right, specify a floating image; the image
is placed at the left or right margin and content flows around it. To place
content below the image, use
as appropriate.
The vertical-align and float properties of Cascading Style Sheets provide
more flexible methods of aligning images.
The BORDER attribute, deprecated in HTML 4.0, specifies the width of the
image's border. Specifying BORDER=0 will eliminate the border around a linked
image in most browsers, though some allow the user to override this. Authors
should only use BORDER=0 if the image would be clearly recognizable as a link,
or as a method of de-emphasizing a link. For example:
Web Authoring Reference
The deprecated HSPACE and VSPACE attributes allow an author to suggest
horizontal gutters and vertical gutters, respectively, around the image. The
value must be in pixels and applies to both sides of the image. Style sheets
provide more flexibility in specifying the space around images.
The USEMAP attribute is used with client-side image maps to give the location
of the map definition. While this value may be a full URI--allowing a single
map definition to be applied to multiple pages-- Netscape Navigator will only
find map definitions in the same file, effectively limiting the USEMAP value
to a fragment identifier such as "#map".
The ISMAP attribute is used with server-side image maps. When the ISMAP
attribute is included with a linked image and the user clicks the image, the
image coordinates clicked are sent to the server, from which a location can be
returned. The method of handling the coordinates is server-dependent, but the
NCSA server's method is most common.
Server-side image maps are better supported than client-side image maps, but
almost all browsers today support both methods. Client-side image maps are
generally preferred since they do not require an extra request to the server
(and so are faster), and since they allow a usable menu to be provided to
text-only users. Using both methods in combination is a good approach, since
browsers supporting client-side image maps will use that method while older
browsers will use the server-side image map. An example follows:
A MAP element named map would have to be included in the same document.
═══ 1.5.47. INPUT - Form input ═══
INPUT - Form Input
Syntax
Attribute Specifications
o TYPE=[ text | password | checkbox | radio | submit | reset | file |
hidden | image | button ] (type of input)
o NAME= CDATA (key in submitted form)
o VALUE= CDATA (value of input)
o CHECKED (check radio button or checkbox)
o SIZE= CDATA (suggested number of characters for text input)
o MAXLENGTH= Number (maximum number of characters for text input)
o SRC= URI (source for image)
o ALT= CDATA (alternate text for image input)
o USEMAP= URI (client-side image map)
o ALIGN=[ top | middle | bottom | left | right ] (alignment of image input)
o DISABLED (disable element)
o READONLY (prevent changes)
o ACCEPT= ContentTypes (media types for file upload)
o ACCESSKEY= Character (shortcut key)
o TABINDEX= Number (position in tabbing order)
o ONFOCUS= Script (element received focus)
o ONBLUR= Script (element lost focus)
o ONSELECT= Script (element text selected)
o ONCHANGE= Script (element value changed)
o common attributes
Contents
Empty
Contained in
Block-level elements, inline elements except BUTTON
The INPUT element defines a form control for the user to enter input. While
INPUT is most useful within a FORM, HTML 4.0 allows INPUT in any block-level
or inline element other than BUTTON. However, Netscape Navigator will not
display any INPUT elements outside of a FORM.
When a form is submitted, the current value of each INPUT element within the
FORM is sent to the server as name/value pairs. The INPUT element's NAME
attribute provides the name used. The value sent depends on the type of form
control and on the user's input.
The type of form control defined by INPUT is given by the TYPE attribute.
The default TYPE is text, which provides a single-line text input field. The
VALUE attribute specifies the initial value for the text field. The SIZE and
MAXLENGTH attributes suggest the number of characters and maximum number of
characters, respectively, of the text field.
While the MAXLENGTH attribute can be an effective guide to the user, authors
should not depend on the enforcement of a maximum number of characters by the
client. A user could copy the HTML document, remove the MAXLENGTH attribute,
and submit the form. Thus authors of form handlers should ensure that any
necessary input length checks are repeated on the server-side.
The password input type is a variation on the text type. The only difference
is that the input characters are masked, typically by a series of asterisks, to
protect sensitive information from onlookers. Note, however, that the actual
value is transmitted to the server as clear text, so password inputs do not
provide sufficient security for credit card numbers or other highly sensitive
information.
The following example uses text and password fields with the LABEL element
to bind text labels to the INPUT elements:
The boolean READONLY attribute, new in HTML 4.0 and poorly supported by
current browsers, prevents the user from editing the content of the text or
password input types. Read-only elements are still submitted with the form.
The DISABLED attribute, which applies to all input types but is also poorly
supported, disables the control. Disabled elements are read-only elements with
the added restrictions that the values are not submitted with the form, the
elements cannot receive focus, and the elements are skipped when navigating the
document by tabbing.
The radio and checkbox input types provide switches that can be turned on and
off by the user. The two types differ in that radio buttons are grouped (by
specifying the same NAME attribute on each INPUT) so that only one radio
button in a group can be selected at any time. Checkboxes can be checked
without changing the state of other checkboxes with the same NAME. The VALUE
attribute, required for radio buttons and checkboxes, gives the value of the
control when it is checked. The boolean CHECKED attribute specifies that the
control is initially checked.
Some browsers require one radio button in a group to be selected at all times.
To ensure that an appropriate default choice is made, authors may wish to
define one of the radio INPUT elements as CHECKED.
In the following example, only one payment method may be selected by the user
since the radio buttons have the same NAME:
Please indicate your method of payment:
The file input type creates a field through which users can upload files from
their local computer or network. The VALUE attribute specifies the name of the
initial file, but it is typically ignored by browsers as a security precaution.
The ACCEPT attribute gives a comma-separated list of media types accepted,
allowing the browser to filter out inappropriate files. Current browsers
generally ignore the ACCEPT attribute.
A form that includes a file INPUT must specify METHOD=post and
ENCTYPE="multipart/form-data" in the
The hidden input type allows authors to include form data without having it
rendered to the user. This is particularly useful in form applications that
span several HTML documents; user input can be carried from form to form by
hidden INPUTs. Some generalized CGI scripts use hidden INPUTs to define
variables for the script, as in the following example, which defines a
recipient and subject for the e-mailed contents of a form:
Note that the fields are "hidden" in the sense that they are not rendered by
the browser. Anyone can still view the HTML document's source to find the
"hidden" fields.
The TYPE value reset defines a button by which the user can reset the form to
its initial values. The optional VALUE attribute of a reset button overrides
the browser's default text for the button.
The submit input type defines a button for submitting the form. As with
reset, the optional VALUE attribute provides the text of the button. The
presence of the NAME attribute will cause the browser to send a name/value pair
for the submit button if it is used to submit the form. This allows authors to
provide multiple submit buttons and have the form handler take a different
action depending on the submit button used.
The image input type specifies a graphical submit button. The SRC attribute
must be included to specify the URI of the image. The ALT attribute should
be used to give replacement text for those not loading images. ALT is a new
addition in HTML 4.0; many browsers rely on either the NAME or VALUE
attribute as alternate text, so authors should use all three attributes for the
same purpose where possible. The topic of graphical submit buttons for text
users is discussed in detail in the article INPUT TYPE=IMAGE for text users?.
When the graphical submit button is clicked, the coordinates of the click are
sent with the form submission as name.x=x-value and name.y=y-value where name
is the value of the NAME attribute, x-value is the click's pixels from the
left of the image, and y-value is the click's pixels from the top of the
image. The USEMAP attribute combined with TYPE=image defines a client-side
image map that can be used with client-side scripting, but this method is
poorly supported. The USEMAP attribute gives the URI of the defining MAP.
The deprecated ALIGN attribute specifies the alignment of the graphical
submit button. The values top, middle, and bottom specify the button's
position with respect to surrounding content on its left and right. The values
left and right specify a floating button; the image is placed at the left or
right margin and content flows around it. To place content below the button,
use
as appropriate.
The vertical-align and float properties of Cascading Style Sheets provide
more flexible methods of aligning buttons.
The input type button specifies a push button for use with client-side
scripting. The VALUE attribute gives the text label of the button. The
ONCLICK attribute is typically used to define the action taken when the button
is activated. An example follows:
In this example, the toggle() function, which would be defined earlier in a
SCRIPT element, will be executed when the button is clicked. Since the button
is only useful with client-side scripting enabled, authors should usually
output the tag using the scripting language to avoid
providing a non-functioning button to some users. A more complete version of
the previous example would thus be as follows:
The BUTTON element allows richer labels for submit, reset, and push buttons,
but a lack of browser support makes INPUT a more reliable choice at this time.
The ACCESSKEY and TABINDEX attributes apply to all input types except hidden.
ACCESSKEY specifies a single Unicode character as a shortcut key for giving
focus to the form control. Authors can set the access key on the INPUT
element or the LABEL element associated with it. Entities (e.g. é)
may be used as the ACCESSKEY value.
The TABINDEX attribute specifies a number between 0 and 32767 to indicate the
tabbing order of the element. A form control with TABINDEX=0 or no TABINDEX
attribute will be visited after any elements with a positive TABINDEX. Among
positive TABINDEX values, the lower number receives focus first. In the case
of a tie, the element appearing first in the HTML document takes precedence.
The INPUT element also takes a number of attributes to specify client-side
scripting actions for various events. In addition to the core events common
to most elements, INPUT accepts the following event attributes:
o ONFOCUS, when the element receives focus;
o ONBLUR, when the element loses focus;
o ONSELECT, when text in an input of type text or password is selected;
o ONCHANGE, when the element loses focus and its value has changed since it
received focus.
═══ 1.5.48. INS - Inserted text ═══
INS - Inserted Text
Syntax
...
Attribute Specifications
o CITE= URI (reason for insertion)
o DATETIME= Datetime (date and time of insertion)
o common attributes
Contents
Inline elements, block-level elements
Contained in
Inline elements, block-level elements
The INS element contains content that has been inserted. This element is
useful in marking changes from one version of a document to the next. Through
style sheets, authors can suggest an appropriate rendering, such as rendering
the inserted content in italics, a different color, or a different voice.
INS may be used as either a block-level element or an inline element. If
used as an inline element (e.g., within a P), then INS may not contain any
block-level elements.
The optional CITE attribute of INS gives a URI with information on why the
content was inserted. A brief explanation for the insertion can be given with
the TITLE attribute, which may be rendered as a "tooltip" by some browsers.
The optional DATETIME attribute specifies the date and time of the insertion.
The value is case-sensitive and of the form YYYY-MM-DDThh:mm:ssTZD. See the
values section for a full explanation of this format.
An example follows:
The CENTER element defines a block whose
contents are centered horizontally on visual browsers.
Note that CENTER is deprecated in HTML 4.0.
═══ 1.5.49. ISINDEX - Input prompt ═══
ISINDEX - Input Prompt
Syntax
If the question does not apply to you, enter
N/A.
═══ 1.5.51. LABEL - Form field label ═══
LABEL - Form Field Label
Syntax
Attribute Specifications
o FOR= IDREF (associated form field)
o ACCESSKEY= Character (shortcut key)
o ONFOCUS= Script (element received focus)
o ONBLUR= Script (element lost focus)
o common attributes
Contents
Inline elements except LABEL
Contained in
Block-level elements, inline elements except BUTTON
The LABEL element associates a label with a form control. By associating
labels with form controls, authors give important hints to users of speech
browsers while also allowing visual browsers to duplicate common GUI features
(e.g., the ability to click on a text label to select a radio button or
checkbox).
Each LABEL element is associated with exactly one form control. The element's
content is the label of the form control and may include inline elements such
as IMG and STRONG.
The FOR attribute explicitly specifies the control associated with the LABEL.
The value of the FOR attribute must match the value of the associated form
control's ID attribute. In the absence of the FOR attribute, the LABEL
must contain the associated form control. This method of implicit association
is convenient in many cases, but not an option when the form control and its
label are in different table cells, paragraphs, or divisions. The following
example illustrates both explicit and implicit label associations:
The ACCESSKEY attribute, used throughout the preceding example, specifies a
single Unicode character as a shortcut key for giving focus to the LABEL, which
passes the focus on to the associated form control. Entities (e.g. é)
may be used as the ACCESSKEY value.
The LABEL element also takes a number of attributes to specify client-side
scripting actions for various events. In addition to the core events common
to most elements, LABEL accepts the following event attributes:
o ONFOCUS, when the element receives focus;
o ONBLUR, when the element loses focus.
═══ 1.5.52. LEGEND - Fieldset caption ═══
LEGEND - Fieldset Caption
Syntax
Attribute Specifications
o ACCESSKEY= Character (shortcut key)
o ALIGN=[ top | bottom | left | right ] (alignment relative to fieldset)
o common attributes
Contents
Inline elements
Contained in
FIELDSET
The LEGEND element defines a caption for form controls grouped by the
FIELDSET element. The LEGEND element must be at the start of a FIELDSET,
before any other elements.
While the LEGEND element is not widely supported by current browsers, it can
still be used safely if a block-level element immediately follows the LEGEND.
Combined with careful use of FIELDSET, this will cause non-supporting browsers
to render the caption as its own paragraph. Elements such as STRONG, B, and
BIG could also be used to help express the meaning of LEGEND to
non-supporting browsers.
An example follows:
LEGEND's ACCESSKEY attribute, used throughout the preceding example, specifies
a single Unicode character as a shortcut key for giving focus to the LEGEND,
allowing the user to quickly jump to a group of form controls. Entities (e.g.
é) may be used as the ACCESSKEY value.
The deprecated ALIGN attribute of LEGEND suggests where the caption should
be positioned relative to the FIELDSET on visual browsers. Possible values
are top, bottom, left, and right. While ALIGN is deprecated, no alternative
currently exists in Cascading Style Sheets.
═══ 1.5.53. LI - List item ═══
LI - List Item
Syntax
...
Attribute Specifications
o TYPE=[ disc | square | circle | 1 | a | A | i | I ] (style of list item
marker)
o VALUE= Number (number in sequence)
o common attributes
Contents
Inline elements, block-level elements (except for LIs used within
DIR and MENU, which do not allow block-level elements)
Contained in
OL, UL, DIR, MENU
The LI element defines a list item. The element must be contained within
DIR, MENU, OL or UL.
Unless used with the deprecated MENU or DIR elements, LI may contain
block-level elements, including H2, TABLE, UL, and OL. This allows OL and
UL to be nested, as in the following example:
-
HTML Document Type Definitions
-
SGML Character Entity References
When used with MENU and DIR, LI may not contain block-level elements, and
lists cannot be nested.
The deprecated TYPE attribute of LI suggests the rendering of the list item
marker. Possible values are as follows:
o Case-insensitive values for LI within a UL, DIR, or MENU:
- disc (a filled-in circle)
- square (a square outline)
- circle (a circle outline)
o Case-sensitive values for LI within an OL:
- 1 (decimal numbers: 1, 2, 3, 4, 5, ...)
- a (lowercase alphabetic: a, b, c, d, e, ...)
- A (uppercase alphabetic: A, B, C, D, E, ...)
- i (lowercase Roman numerals: i, ii, iii, iv, v, ...)
- I (uppercase Roman numerals: I, II, III, IV, V, ...)
Style sheets provide greater flexibility in suggesting list item styles. The
list-style property of CSS includes the added abilities to suppress list item
markers, use images as markers, and more.
LI's VALUE attribute specifies the number of the list item when used with an
OL. The number must be given as an integer, though the list item marker may be
rendered in another form (for example, as a Roman numeral). Any LI element
following in the same list will take its default sequence number based on the
first preceding VALUE attribute. VALUE is deprecated in HTML 4.0, but no
substitute currently exists in CSS.
═══ 1.5.54. LINK - Document relationship ═══
LINK - Document Relationship
Syntax
Attribute Specifications
o REL= LinkTypes (relationship to link)
o REV= LinkTypes (relationship from link)
o HREF= URI (hypertext reference)
o TYPE= ContentType (content-type of link)
o TARGET= FrameTarget (frame to render link in)
o MEDIA= MediaDesc (media appropriate for link)
o HREFLANG= LanguageCode (language of link)
o CHARSET= Charset (character encoding of link)
o common attributes
Contents
Empty
Contained in
HEAD
The LINK element defines document relationships. Any number of LINK elements
may be contained in the HEAD of a document. Many browsers lack support for
LINK, so authors should not depend on the browser making the links available to
the user.
The REL and REV attributes define the nature of the relationship between the
documents and the linked resource. REL defines a link relationship from the
current document to the linked resource while REV defines a relationship in
the opposite direction. For example,
indicates that foo.html is a glossary for the current document while
indicates that the current document is a subsection of bar.html. The value of
the REL and REV attributes is a space-separated list of link types.
Commonly used relationships include the next or previous document in a
sequence, the starting page in a collection of documents, a document with
copyright information, and information about the author. A document could
define these relationships as follows:
While the value of REL and REV is case-insensitive, the Lynx browser renders
the relationship exactly as given by the author. Authors should therefore be
consistent in their case, and may wish to capitalize the first letter while
using lowercase for the rest.
Authors can also use the LINK element to apply an external style sheet.
REL=StyleSheet specifies a persistent or preferred style while REL="Alternate
StyleSheet" defines an alternate style. A persistent style is one that is
always applied when style sheets are enabled. The absence of the TITLE
attribute indicates a persistent style.
A preferred style is one that is automatically applied. The combination of
REL=StyleSheet and a TITLE attribute specifies a preferred style. Authors
cannot specify more than one preferred style.
An alternate style is indicated by REL="Alternate StyleSheet". The user could
choose to replace the preferred style sheet with an alternate one, though
current browsers generally lack the ability to choose alternate styles.
A single style may also be given through multiple style sheets:
In this example, three style sheets are combined into one "Contemporary" style
that is applied as a preferred style sheet. To combine multiple style sheets
into a single style, each style sheet's LINK must use the same TITLE.
LINK's MEDIA attribute specifies the media for which the linked resource is
designed. With REL=StyleSheet, this allows authors to restrict a style sheet
to certain output devices, such as printers or aural browsers. The attribute's
value is a comma-separated list of media descriptors. The following media
descriptors are defined in HTML 4.0 and are case-sensitive:
o screen (the default), for non-paged computer screens;
o tty, for fixed-pitch character grid displays (such as the display used by
Lynx);
o tv, for television-type devices with low resolution and limited
scrollability;
o projection, for projectors;
o handheld, for handheld devices (characterized by a small, monochrome display
and limited bandwidth);
o print, for output to a printer;
o braille, for braille tactile feedback devices;
o aural, for speech synthesizers;
o all, for all devices.
Netscape Navigator 4.x incorrectly ignores any style sheet linked with a MEDIA
value other than screen. For example, MEDIA="screen, projection" will cause
the style sheet to be ignored by Navigator 4.x, even if the presentation device
is a computer screen. Navigator 4.x also ignores style sheets declared with
MEDIA=all. Most other browsers ignore the MEDIA attribute.
The optional HREFLANG and CHARSET attributes of LINK give the language and
character encoding, respectively, of the link. The language should be
specified according to RFC 1766; examples include en for English, en-US for
American English, and ja for Japanese. Examples of character encodings
include ISO-8859-1, SHIFT_JIS, and UTF-8.
The Alternate link relationship defines an alternate version of the document.
Translations of a page can be identified by using REL=Alternate along with the
HREFLANG attribute. Versions of the page tailored for specific media can be
provided by combining REL=Alternate with the MEDIA attribute. Some examples
follow:
Note that the LANG and DIR attributes apply to the text of the TITLE
attribute, not to the content of the link.
The TARGET attribute is used with frames to specify in which frame the link
should be rendered. If no frame with such a name exists, the link is rendered
in a new window unless overridden by the user. Special frame names begin with
an underscore:
o _blank renders the link in a new, unnamed window
o _self renders the link in the current frame (useful for overriding a BASE
TARGET)
o _parent renders the link in the immediate FRAMESET parent
o _top renders the link in the full, unframed window
═══ 1.5.55. MAP - Image map ═══
MAP - Image Map
Syntax
Attribute Specifications
o NAME= CDATA (name of map)
o common attributes
Contents
One or more block-level elements or one or more AREA elements
Contained in
Inline elements, block-level elements
The MAP element defines a client-side image map for use with an IMG or
OBJECT. MAP's required NAME attribute is used as an anchor for the USEMAP
attribute of the IMG or OBJECT. While a MAP element can define image maps
embedded in other files, browsers typically only support client-side image maps
with the MAP in the same file as the image.
MAP was originally defined to take one or more AREA elements that specified
the coordinates of a clickable region on the image. An example follows:
HTML 4.0 extends the MAP element to take one or more block-level elements as
an alternative to using AREA elements. Combined with the OBJECT element,
this allows rich alternative content for those not loading images. However,
due to poor and buggy browser support for OBJECT, client-side image maps
through the IMG element are more reliable.
When MAP is given within an OBJECT, its contents are not rendered on
image-loading browsers. MAP may also be used outside the OBJECT element so
that its contents are rendered.
The following example gives two images, one an alternate if the first type of
image is not supported. The images share a single image map definition, which
is included within the OBJECT element. The MAP element contains a menu of
links to be rendered on browsers not loading images.
═══ 1.5.56. MENU - Menu list ═══
MENU - Menu List
Syntax
Attribute Specifications
o COMPACT (compact display)
o common attributes
Contents
One or more LI elements that cannot contain block-level elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The MENU element defines a menu list. The element contains one or more LI
elements that define the actual items of the list. The LI elements must not
contain block-level elements, which prevents MENUs from being nested.
The COMPACT attribute suggests that visual browsers render the list compactly,
perhaps with reduced spacing between items. This attribute is not well
supported among browsers.
MENU is deprecated in HTML 4.0 in favor of UL.
═══ 1.5.57. META - Metadata ═══
META - Metadata
Syntax
Attribute Specifications
o NAME= Name (property name)
o HTTP-EQUIV= Name (HTTP response header name)
o CONTENT= CDATA (associated data)
o SCHEME= CDATA (form of data)
o internationalization attributes (for the CONTENT)
Contents
Empty
Contained in
HEAD
The META element provides metadata such as a document's keywords,
description, and author. Any number of META elements may be contained in the
HEAD of a document.
META's NAME attribute provides a property name while the CONTENT attribute
gives the corresponding value. The CONTENT attribute value may contain text
and entities, but it may not contain HTML tags.
The optional SCHEME attribute gives the format of the property value. For
example, a date property may require SCHEME="Month-Day-Year" to disambiguate
the date from other formats such as SCHEME="Day-Month-Year".
There is no standard list of META properties, so authors may define whatever
metadata they like. The following example defines the author of the document:
Some search engines use keywords and description properties, giving extra
weight to a document's keywords and providing its description with the link to
the document. Example:
To avoid being truncated by search engines, the description should be brief--no
more than 200 characters. Keywords are separated by commas and may be
considered case sensitive by search engines. If the same keywords are repeated
too often in the META element, some search engines will not index the
document. Search engines typically only process the first 1000 characters of
the keywords list.
Some search engines also support the robots property for indicating whether a
document should be indexed and whether its links should be followed. The
associated CONTENT value is a comma-separated list of case-insensitive
directives:
o index specifies that the page should be indexed while noindex specifies
that it should not be indexed;
o follow specifies that the page's links should be followed while nofollow
specifies that they should not be followed;
o all is equivalent to index,follow (the default value);
o none is equivalent to noindex,nofollow.
For example, the following META element tells search engines and other robots
not to index the page but to follow links on it:
Few search engines support the robots property at this time. For greater
compliance by robots, authors should use the Robots Exclusion Protocol if
possible.
The HTTP-EQUIV attribute may be used in place of the NAME attribute to
indicate that the property is an HTTP header. Some servers will send the HTTP
header specified in the META element, and browsers often recognize the header
even when it is not sent by the server. Examples:
sets the expiry date of the document.
sets the client-side scripting language for inline scripts to JavaScript.
sets the style language for inline styles to CSS.
sets the character encoding for the document to SHIFT_JIS (a Japanese
encoding). Note that using META for this purpose rather than a true HTTP
header causes some browsers to redraw the page after initially displaying it.
tells the browser to load http://www.htmlhelp.com/ 10 seconds after the current
document has finished loading. Not all browsers support this, so authors
should provide an alternate means of moving to the new page where necessary.
The Refresh header is sometimes used for "splash screens" or when a page has
moved, but the technique is not very effective since users may not even be
looking at the window that is to be refreshed and since it messes up the user's
history on many browsers. Some search engines penalize pages that use a
Refresh of a few seconds or less.
═══ 1.5.58. NOFRAMES - Frames alternate content ═══
NOFRAMES - Frames Alternate Content
Syntax
...<NOFRAMES>
Attribute Specifications
o common attributes
Contents
o In HTML 4.0 Transitional: inline elements, block-level elements
o In HTML 4.0 Frameset: one BODY element that must not contain any
NOFRAMES elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, FRAMESET, IFRAME, INS, LI, MAP, NOSCRIPT, OBJECT, TD, TH
The NOFRAMES element contains content that should only be rendered when frames
are not displayed. NOFRAMES is typically used in a Frameset document to
provide alternate content for browsers that do not support frames or have
frames disabled.
When used within a FRAMESET, NOFRAMES must contain a BODY element. There
must not be any NOFRAMES elements contained within this BODY element.
A meaningful NOFRAMES element should always be provided in a Frameset document
and should at the very least contain links to the main frame or frames.
NOFRAMES should not contain a message telling the user to upgrade his or her
browser. Some browsers support frames but allow the user to disable them.
Various methods of automatically creating non-frames content exist. See Frames
design guidelines: automatic no-frames content for more details.
An example follows:
<FRAMESET ROWS="*,100">
<FRAMESET COLS="40%,*">
<FRAME NAME="Menu" SRC="nav.html" TITLE="Menu">
<FRAME NAME="Content" SRC="main.html" TITLE="Content">
</FRAMESET>
<FRAME NAME="Ad" SRC="ad.html" TITLE="Advertisement">
<NOFRAMES>
<BODY>
<H1>Table of Contents</H1>
<UL>
<LI>
<A HREF="reference/html40/">HTML 4.0 Reference</A>
</LI>
<LI>
<A HREF="reference/wilbur/">HTML 3.2 Reference</A>
</LI>
<LI>
<A HREF="reference/css/">CSS Guide</A>
</LI>
</UL>
<P>
<IMG SRC="ad.gif" ALT="Ad: Does your bank charge too much?">
</P>
</BODY>
In HTML 4.0 Transitional, the NOFRAMES element is also permitted within most
block-level elements. This allows authors to include content, such as
navigation aids, that should only be displayed if the document is not being
viewed within a frameset. Such use helps to ensure that a frame could stand on
its own if bookmarked or accessed through a search engine while not burdening
the frames user with duplicate content. However, most browsers do not support
this use of NOFRAMES and will always display the content.
═══ 1.5.59. NOSCRIPT - Alternate script content ═══
NOSCRIPT - Non-script Content
Syntax
Attribute Specifications
o common attributes
Contents
Block-level elements, inline elements
Contained in
APPLET, BLOCKQUOTE, BODY, BUTTON, CENTER, DD, DEL, DIV, FIELDSET,
FORM, IFRAME, INS, LI, MAP, NOFRAMES, NOSCRIPT, OBJECT, TD, TH
The NOSCRIPT element provides alternate content for a client-side script that
was not executed. A script will fail to execute if the browser does not
support the scripting language or if the user has disabled client-side
scripting. NOSCRIPT should follow the SCRIPT element for which it provides
alternate content.
Note that most browsers will fail to render the contents of NOSCRIPT if the
scripting language is not supported and the user has enabled client-side
scripting. Most browsers will only render NOSCRIPT when the user has disabled
client-side scripting.
Also note that Netscape Navigator 2.x supports JavaScript 1.0 but still
renders all NOSCRIPT content.
Since client-side scripts usually provide dynamic interactivity that cannot be
replaced by static content, the NOSCRIPT element is generally not useful.
Authors should try to use client-side scripts as optional enhancements that are
not integral components of the Web page. In the case of form validation, any
error checking done by the client-side script should be repeated by the CGI
script or Java servlet that handles the submission at the server.
═══ 1.5.60. OBJECT - Object ═══
OBJECT - Embedded Object
Syntax
Attribute Specifications
o DATA= URI (object data)
o CLASSID= URI (location of implementation)
o ARCHIVE= CDATA (archive files)
o CODEBASE= URI (base URI for CLASSID, DATA, ARCHIVE)
o WIDTH= Length (object width)
o HEIGHT= Length (object height)
o NAME= CDATA (name for form submission)
o USEMAP= URI (client-side image map)
o TYPE= ContentType (content-type of object)
o CODETYPE= ContentType (content-type of code)
o STANDBY= Text (message to show while loading)
o TABINDEX= NUMBER (position in tabbing order)
o DECLARE (do not instantiate object)
o ALIGN=[ top | middle | bottom | left | right ] (object alignment)
o BORDER= Length (link border width)
o HSPACE= Pixels (horizontal gutter)
o VSPACE= Pixels (vertical gutter)
o common attributes
Contents
PARAM elements followed by block-level elements and/or inline
elements
Contained in
HEAD, inline elements, block-level elements except PRE
The OBJECT element is used to include objects such as images, videos, Java
applets, and VRML worlds. OBJECT is intended to replace the more specific
IMG and APPLET elements, as well as the proprietary EMBED and BGSOUND
elements, though a lack of browser support and severe bugs in supporting
browsers make the other elements a better choice for the time being.
OBJECT's DATA attribute specifies the URI of the embedded object. Relative
URIs are interpreted with respect to the CODEBASE attribute if it is given.
The WIDTH and HEIGHT attributes define the dimensions of the object. The
value may be given in pixels or as a percentage of the parent element's width
or height. Most browsers require the WIDTH and HEIGHT attributes for all
objects embedded using OBJECT.
The CLASSID may be used to specify an implementation for the object. Java
applets, Python applets, and ActiveX controls all provide implementations for
the embedded object, and so are specified with the CLASSID attribute, as in
the following example:
This example also demonstrates the use of alternate content for browsers that
cannot display the embedded object. In the example, a Yahtzee game written in
Python is used if the browser supports it. A Java version is provided as an
alternate for browsers that do not support Python applets. An image is given
for browsers that cannot show the Java or Python applets, and plain text is
used as a final alternate if images are not loaded. Note that OBJECT is
backwards compatible with pre-HTML 4.0 browsers since they will ignore the
