ABCD Interaktív Magazin 1995 #2/ABCD.ISO/abcd/muhely/html/bguide

Text File | 1995-04-12 | 31.3 KB | 893 lines

A Beginner's Guide to HTML

This is a primer for producing documents in HTML, the markup language used by
the World Wide Web.

   Acronym Expansion
   What This Primer Doesn't Cover
   Creating HTML Documents
      The Minimal HTML Document
      Basic Markup Tags
         Titles
         Headings
         Paragraphs
      Linking to Other Documents
         Relative Links Versus Absolute Pathnames
         Uniform Resource Locator
         Anchors to Specific Sections in Other Documents
         Anchors to Specific Sections Within the Current Document
   Additional Markup Tags
      Lists
         Unnumbered Lists
         Numbered Lists
         Definition Lists
         Nested Lists
      Preformatted Text
      Extended Quotes
      Addresses
   Character Formatting
      Physical Versus Logical: Use Logical Tags When Possible
         Logical Styles
         Physical Styles
      Using Character Tags
      Special Characters
         Escape Sequences
         Forced Line Breaks
         Horizontal Rules
   In-line Images
      Alternate Text for Viewers That Can't Display Images
   External Images, Sounds, and Animations
   Troubleshooting
      Avoid Overlapping Tags
      Embed Anchors and Character Tags, But Not Anything Else
      Check Your Links
   A Longer Example
   For More Information
      Fill-out Forms
      Style Guides
      Other Introductory Documents
      Additional References

Acronym Expansion

WWW
   World Wide Web (or Web, for short).
SGML
   Standard Generalized Markup Language -- this is a standard for describing
   markup languages.
DTD
   Document Type Definition -- this is a specific markup language, written using
   SGML.
HTML
   HyperText Markup Language -- HTML is a SGML DTD. In practical terms, HTML is
   a collection of styles (indicated by markup tags) that define the various
   components of a World Wide Web document.

What This Primer Doesn't Cover

This primer assumes that you have:

   at least a passing knowledge of how to use NCSA Mosaic or some other Web
   browser
   a general understanding of how Web servers and client browsers work
   access to a Web server for which you would like to produce HTML documents, or
   that you wish to produce HTML documents for personal use

Creating HTML Documents

HTML documents are in plain (also known as ASCII) text format and can be created
using any text editor (e.g., Emacs or vi on UNIX machines). A couple of Web
browsers (tkWWW for X Window System machines and CERN's Web browser for NeXT
computers) include rudimentary HTML editors in a WYSIWYG environment. There are
also some WYSIWIG editors available now (e.g. HotMetal for Sun Sparcstations,
HTML Edit for Macintoshes). You may wish to try one of them first before delving
into the details of HTML.

  You can preview a document in progress with NCSA Mosaic (and some other
  Web browsers). Open it with the Open Local command under the File menu.

  After you edit the source HTML file, save the changes. Return to NCSA
  Mosaic and Reload the document. The changes are reflected in the on-screen
  display.

The Minimal HTML Document

Here is a bare-bones example of HTML:

    <TITLE>The simplest HTML example</TITLE>
    <H1>This is a level-one heading</H1>
    Welcome to the world of HTML.
    This is one paragraph.<P>
    And this is a second.<P>

Click here to see the formatted version of the example.

HTML uses markup tags to tell the Web browser how to display the text. The above
example uses:

   the <TITLE> tag (and corresponding </TITLE> tag), which specifies the title
   of the document
   the <H1> header tag (and corresponding </H1>)
   the <P> paragraph-separator tag

HTML tags consist of a left angle bracket (<), (a ``less than'' symbol to
mathematicians), followed by name of the tag and closed by a right angular
bracket (>). Tags are usually paired, e.g. <H1> and </H1>. The ending tag looks
just like the starting tag except a slash (/) precedes the text within the
brackets. In the example, <H1> tells the Web browser to start formatting a
level-one heading; </H1> tells the browser that the heading is complete.

The primary exception to the pairing rule is the <P> tag. There is no such thing
as </P>.

NOTE: HTML is not case sensitive. <title> is equivalent to <TITLE> or <TiTlE>.

Not all tags are supported by all World Wide Web browsers. If a browser does not
support a tag, it just ignores it.

Basic Markup Tags

Title

Every HTML document should have a title. A title is generally displayed
separately from the document and is used primarily for document identification
in other contexts (e.g., a WAIS search). Choose about half a dozen words that
describe the document's purpose.

  In the X Window System and Microsoft Windows versions of NCSA Mosaic, the
  Document Title field is at the top of the screen just below the pulldown
  menus. In NCSA Mosaic for Macintosh, text tagged as <TITLE> appears as the
  window title.

Headings

HTML has six levels of headings, numbered 1 through 6, with 1 being the most
prominent. Headings are displayed in larger and/or bolder fonts than normal body
text. The first heading in each document should be tagged <H1>. The syntax of
the heading tag is:

<Hy>Text of heading </Hy >

where y is a number between 1 and 6 specifying the level of the heading.

For example, the coding for the ``Headings'' section heading above is

    <H3>Headings</H3>

Title versus first heading

In many documents, the first heading is identical to the title. For multipart
documents, the text of the first heading should be suitable for a reader who is
already browsing related information (e.g., a chapter title), while the title
tag should identify the document in a wider context (e.g., include both the book
title and the chapter title, although this can sometimes become overly long).

Paragraphs

Unlike documents in most word processors, carriage returns in HTML files aren't
significant. Word wrapping can occur at any point in your source file, and
multiple spaces are collapsed into a single space. (There are couple of
exceptions; space following a <P> or <Hy> tag, for example, is ignored.) Notice
that in the bare-bones example, the first paragraph is coded as

    Welcome to HTML.
    This is the first paragraph. <P>

In the source file, there is a line break between the sentences. A Web browser
ignores this line break and starts a new paragraph only when it reaches a <P>
tag.

Important: You must separate paragraphs with <P>. The browser ignores any
indentations or blank lines in the source text. HTML relies almost entirely on
the tags for formatting instructions, and without the <P> tags, the document
becomes one large paragraph. (The exception is text tagged as ``preformatted,''
which is explained below.) For instance, the following would produce identical
output as the first bare-bones HTML example:

    <TITLE>The simplest HTML example</TITLE><H1>This is a level
    one heading</H1>Welcome to the world of HTML. This is one
    paragraph.<P>And this is a second.<P>

However, to preserve readability in HTML files, headings should be on separate
lines, and paragraphs should be separated by blank lines (in addition to the <P>
tags).

  NCSA Mosaic handles <P> by ending the current paragraph and inserting a
  blank line.

In HTML+, a successor to HTML currently in development, <P> becomes a
``container'' of text, just as the text of a level-one heading is ``contained''
within<H1> ... </H1>:

    <P>
    This is a paragraph in HTML+.
    </P>

The difference is that the </P> closing tag can always be omitted. (That is, if
a browser sees a <P>, it knows that there must be an implied </P> to end the
previous paragraph.) In other words, in HTML+, <P> is a beginning-of-paragraph
marker.

The advantage of this change is that you will be able to specify formatting
options for a paragraph. For example, in HTML+, you will be able to center a
paragraph by coding

    <P ALIGN=CENTER>
    This is a centered paragraph. This is HTML+, so you can't do it yet.

This change won't effect any documents you write now, and they will continue to
look just the same with HTML+ browsers.

Linking to Other Documents

The chief power of HTML comes from its ability to link regions of text (and also
images) to another document. The browser highlights these regions (usually with
color and/or underlines) to indicate that they are hypertext links (often
shortened to hyperlinks or simply links).

HTML's single hypertext-related tag is <A>, which stands for anchor. To include
an anchor in your document:

1. Start the anchor with <A . (There's a space after the A.)
2. Specify the document that's being pointed to by entering the parameter HREF="
   filename" followed by a closing right angle bracket: >
3. Enter the text that will serve as the hypertext link in the current document.
4. Enter the ending anchor tag: </A>.

Here is an sample hypertext reference:

    <A HREF="MaineStats.html">Maine</A>

This entry makes the word ``Maine'' the hyperlink to the document
MaineStats.html, which is in the same directory as the first document. You can
link to documents in other directories by specifying the relative path from the
current document to the linked document. For example, a link to a file
NJStats.html located in the subdirectory AtlanticStates would be:

    <A HREF="AtlanticStates/NJStats.html">New Jersey</A>

These are called relative links. You can also use the absolute pathname of the
file if you wish. Pathnames use the standard UNIX syntax.

Relative Links Versus Absolute Pathnames

In general, you should use relative links, because

1. You have less to type.
2. It's easier to move a group of documents to another location, because the
   relative path names will still be valid.

However, use absolute pathnames when linking to documents that are not directly
related. For example, consider a group of documents that comprise a user manual.
Links within this group should be relative links. Links to other documents
(perhaps a reference to related software) should use full path names. This way,
if you move the user manual to a different directory, none of the links would
have to be updated.

Uniform Resource Locator

The World Wide Web uses Uniform Resource Locators (URLs) to specify the location
of files on other servers. A URL includes the type of resource being accessed
(e.g., gopher, WAIS), the address of the server, and the location of the file.
The syntax is:

scheme://host.domain[:port]/path/filename

where scheme is one of

file
   a file on your local system, or a file on an anonymous FTP server
http
   a file on a World Wide Web server
gopher
   a file on a Gopher server
WAIS
   a file on a WAIS server
news
   an Usenet newsgroup
telnet
   a connection to a Telnet-based service

The port number can generally be omitted. (That means unless someone tells you
otherwise, leave it out.)

For example, to include a link to this primer in your document, you would use

    <A HREF = "http://www.ncsa.uiuc.edu/General/Internet/WWW/HTMLPrimer.html">
    NCSA's Beginner's Guide to HTML</A>

This would make the text ``NCSA's Beginner's Guide to HTML'' a hyperlink to this
document.

For more information on URLs, look at

   WWW Names and Addresses, URIs, URLs, URNs, written by people at CERN
   A Beginner's Guide to URLs, located on the NCSA Mosaic Help menu

Links to Specific Sections in Other Documents

Anchors can also be used to move to a particular section in a document. Suppose
you wish to set a link from document A and a specific section in document B.
(Call this file documentB.html.) First you need to set up a named anchor in
document B. For example, to set up an anchor named ``Jabberwocky'' to document
B, enter

    Here's <A NAME = "Jabberwocky">some text</a>

Now when you create the link in document A, include not only the filename, but
also the named anchor, separated by a hash mark (#).

    This is my <A HREF = "documentB.html#Jabberwocky">link</A> to document B.

Now clicking on the word ``link'' in document A sends the reader directly to the
words ``some text'' in document B.

Links to Specific Sections Within the Current Document

The technique is exactly the same except the filename is omitted.

For example, to link to the Jabberwocky anchor from within the same file
(Document B), use

    This is <A HREF = "#Jabberwocky">Jabberwocky link</A> from within Document B.

Additional Markup Tags

The preceding is sufficient to produce simple HTML documents. For more complex
documents, HTML has tags for several types of lists, preformatted sections,
extended quotations, character formatting, and other items.

Lists

HTML supports unnumbered, numbered, and definition lists.

Unnumbered Lists

To make an unnumbered list,

1. Start with an opening list <UL> tag.
2. Enter the <LI> tag followed by the individual item. (No closing </LI> tag is
   needed.)
3. End with a closing list </UL> tag.

Below an example two-item list:

    <UL>
    <LI> apples
    <LI> bananas
    </UL>

The output is:

   apples
   bananas

The <LI> items can contain multiple paragraphs. Just separate the paragraphs
with the <P> paragraph tags.

Numbered Lists

A numbered list (also called an ordered list, from which the tag name derives)
is identical to an unnumbered list, except it uses <OL> instead of <UL>. The
items are tagged using the same <LI> tag. The following HTML code

    <OL>
    <LI> oranges
    <LI> peaches
    <LI> grapes
    </OL>

produces this formatted output:

1. oranges
2. peaches
3. grapes

Definition Lists

A definition list usually consists of alternating a term (abbreviated as DT) and
a definition (abbreviated as DD). Web browsers generally format the definition
on a new line.

The following is an example of a definition list:

    <DL>
    <DT> NCSA
    <DD> NCSA, the National Center for Supercomputing Applications,
         is located on the campus of the University of Illinois
         at Urbana-Champaign. NCSA is one of the participants in the
         National MetaCenter for Computational Science and Engineering.
    <DT> Cornell Theory Center
    <DD> CTC is located on the campus of Cornell University in Ithaca,
         New York. CTC is another participant in the National MetaCenter
         for Computational Science and Engineering.
    </DL>

The output looks like:

NCSA
   NCSA, the National Center for Supercomputing Applications, is located on the
   campus of the University of Illinois at Urbana-Champaign. NCSA is one of the
   participants in the National MetaCenter for Computational Science and
   Engineering.
Cornell Theory Center
   CTC is located on the campus of Cornell University in Ithaca, New York. CTC
   is another participant in the National MetaCenter for Computational Science
   and Engineering.

The <DT> and <DD> entries can contain multiple paragraphs (separated by <P>
paragraph tags), lists, or other definition information.

Nested Lists

Lists can be arbitrarily nested, although in practice you probably should limit
the nesting to three levels. You can also have a number of paragraphs, each
containing a nested list, in a single list item.

An example nested list:

    <UL>
    <LI> A few New England states:
        <UL>
        <LI> Vermont
        <LI> New Hampshire
        </UL>
    <LI> One Midwestern state:
        <UL>
        <LI> Michigan
        </UL>
    </UL>

The nested list is displayed as

   A few New England states:
      Vermont
      New Hampshire
   One Midwestern state:
      Michigan

Preformatted Text

Use the <PRE> tag (which stands for ``preformatted'') to generate text in a
fixed-width font and cause spaces, new lines, and tabs to be significant. (That
is, multiple spaces are displayed as multiple spaces, and lines break in the
same locations as in the source HTML file.) This is useful for program listings.
For example, the following lines

    <PRE>
      #!/bin/csh
      cd $SCR
      cfs get mysrc.f:mycfsdir/mysrc.f
      cfs get myinfile:mycfsdir/myinfile
      fc -02 -o mya.out mysrc.f
      mya.out
      cfs save myoutfile:mycfsdir/myoutfile
      rm *
    </PRE>

display as

      #!/bin/csh
      cd $SCR
      cfs get mysrc.f:mycfsdir/mysrc.f
      cfs get myinfile:mycfsdir/myinfile
      fc -02 -o mya.out mysrc.f
      mya.out
      cfs save myoutfile:mycfsdir/myoutfile
      rm *

Hyperlinks can be used within <PRE> sections. You should avoid using other HTML
tags within <PRE> sections, however.

Note that because <, >, and & have special meaning in HTML, you have to use
their escape sequences (<, >, and &, respectively) to enter these
characters. See the section Special Characters for more information.

Extended Quotations

Use the <BLOCKQUOTE> tag to include quotations in a separate block on the
screen. Most browsers generally indent to separate it from surrounding text.

An example:

    <BLOCKQUOTE>
    I still have a dream. It is a dream deeply rooted in the
    American dream. <P>
    I have a dream that one day this nation will rise up and
    live out the true meaning of its creed. We hold these truths
    to be self-evident that all men are created equal. <P>
    </BLOCKQUOTE>

The result is:

  I still have a dream. It is a dream deeply rooted in the American dream.

  I have a dream that one day this nation will rise up and live out the true
  meaning of its creed. We hold these truths to be self-evident that all men
  are created equal.

Addresses

The <ADDRESS> tag is generally used to specify the author of a document and a
means of contacting the author (e.g., an email address). This is usually the
last item in a file.

For example, the last line of the online version of this guide is

    <ADDRESS>
    A Beginner's Guide to HTML / NCSA / [e-mail]
    </ADDRESS>

The result is
A Beginner's Guide to HTML / NCSA / [e-mail]

NOTE: <ADDRESS> is not used for postal addresses. See ``Forced Line Breaks'' on
page 10 to see how to format postal addresses.

Character Formatting

You can code individual words or sentences with special styles. There are two
types of styles: logical and physical. Logical styles tag text according to its
meaning, while physical styles specify the specific appearance of a section. For
example, in the preceding sentence, the words ``logical styles'' was tagged as a
``definition.'' The same effect (formatting those words in italics), could have
been achieved via a different tag that specifies merely ``put these words in
italics.''

Physical Versus Logical: Use Logical Styles When Possible

If physical and logical styles produce the same result on the screen, why are
there both? We devolve, for a couple of paragraphs, into the philosophy of SGML,
which can be summed in a Zen-like mantra: ``Trust your browser.''

In the ideal SGML universe, content is divorced from presentation. Thus, SGML
tags a level-one heading as a level-one heading, but does not specify that the
level-one heading should be, for instance, 24-point bold Times centered on the
top of a page. The advantage of this approach (it's similar in concept to style
sheets in many word processors) is that if you decide to change level-one
headings to be 20-point left-justified Helvetica, all you have to do is change
the definition of the level-one heading in the presentation device (i.e., your
World Wide Web browser).

The other advantage of logical tags is that they help enforce consistency in
your documents. It's easier to tag something as <H1> than to remember that
level-one headings are 24-point bold Times or whatever. The same is true for
character styles. For example, consider the <STRONG> tag. Most browsers render
it in bold text. However, it is possible that a reader would prefer that these
sections be displayed in red instead. Logical styles offer this flexibility.

Logical Styles

<DFN>
   for a word being defined. Typically displayed in italics. (NCSA Mosaic is a
   World Wide Web browser.)
<EM>
   for emphasis. Typically displayed in italics. (Watch out for pickpockets.)
<CITE>
   for titles of books, films, etc. Typically displayed in italics. (A
   Beginner's Guide to HTML)
<CODE>
   for snippets of computer code. Displayed in a fixed-width font. (The
   <stdio.h> header file)
<KBD>
   for user keyboard entry. Should be displayed in a bold fixed-width font, but
   many browsers render it in the plain fixed-width font. (Enter passwd to
   change your password.)
<SAMP>
   for computer status messages. Displayed in a fixed-width font. (Segmentation
   fault: Core dumped.)
<STRONG>
   for strong emphasis. Typically displayed in bold. (Important)
<VAR>
   for a ``metasyntactic'' variable, where the user is to replace the variable
   with a specific instance. Typically displayed in italics. (rm filename
   deletes the file.)

Physical Styles

<B>
   bold text
<I>
   italic text
<TT>
   typewriter text, e.g. fixed-width font.

Using Character Tags

To apply a character style,

1. Start with <tag>, where tag is the desired character formatting tag, to
   indicate the beginning of the tagged text.
2. Enter the tagged text.
3. End the passage with </tag>.

Special Characters

Escape Sequences

Four characters of the ASCII character set -- the left angle bracket (<), the
right angle bracket (>), the ampersand (&) and the double quote (") -- have
special meaning within HTML and therefore cannot be used ``as is'' in text. (The
angle brackets are used to indicate the beginning and end of HTML tags, and the
ampersand is used to indicate the beginning of an escape sequence.)

To use one of these characters in an HTML document, you must enter its escape
sequence instead:

<
   the escape sequence for <
>
   the escape sequence for >
&
   the escape sequence for &
"
   the escape sequence for "

Additional escape sequences support accented characters. For example:

ö
   the escape sequence for a lowercase o with an umlaut: ÷
ñ
   the escape sequence for a lowercase n with an tilde: ±
È
   the escape sequence for an uppercase E with a grave accent: ╚

A full list of supported characters can be found at CERN.

NOTE: Unlike the rest of HTML, the escape sequences are case sensitive. You
cannot, for instance, use < instead of <.

Forced Line Breaks

The <BR> tag forces a line break with no extra space between lines. (By
contrast, most browsers format the <P> paragraph tag with an additional blank
line to more clearly indicate the beginning the new paragraph.)

One use of <BR> is in formatting addresses:

    National Center for Supercomputing Applications<BR>
    605 East Springfield Avenue<BR>
    Champaign, Illinois 61820-5518<BR>

Horizontal Rules

The <HR> tag produces a horizontal line the width of the browser window.

In-line Images

Most Web browsers can display in-line images (that is, images next to text) that
are in X Bitmap (XBM) or GIF format. Each image takes time to process and slows
down the initial display of the document, so generally you should not include
too many or overly large images.

To include an in-line image, use

    <IMG SRC=image_URL>

where image_URL is the URL of the image file. The syntax for IMG SRC URLs is
identical to that used in an anchor HREF. If the image file is a GIF file, then
the filename part of image_URL must end with .gif. Filenames of X Bitmap images
must end with .xbm.

            By default the bottom of an image is aligned with the text as shown
in this paragraph.

             Add the ALIGN=TOP option if you want the browser to align adjacent
text with the top of the image as shown in this paragraph. The full in-line
image tag with the top alignment is:

    <IMG ALIGN=top SRC=image_URL>

             ALIGN=MIDDLE aligns the text with the center of the image.

Alternate Text for Browsers That Can't Display Images

Some World Wide Web browsers, primarily those that run on VT100 terminals,
cannot display images. The ALT option allows you to specify text to be displayed
when an image cannot be. For example:

    <IMG SRC = "UpArrow.gif" ALT = "Up">

where UpArrow.gif is the picture of an upward pointing arrow. With NCSA Mosaic
and other graphics-capable viewers, the user sees the up arrow graphic. With a
VT100 browser, such as lynx, the user sees the word ``Up.''

External Images, Sounds, and Animations

You may want to have an image open as a separate document when a user activates
a link on either a word or a smaller, in-line version of the image included in
your document. This is considered an external image and is useful if you do not
wish to slow down the loading of the main document with large in-line images.

To include a reference to an external image, use

    <A HREF = image_URL>link anchor</A>

Use the same syntax is for links to external animations and sounds. The only
difference is the file extension of the linked file. For example,

<A HREF = "QuickTimeMovie.mov">link anchor</A>

specifies a link to a QuickTime movie. Some common file types and their
extensions are:

File Type
   Extension
Plain text
   .txt
HTML document
   .html
GIF image
   .gif
TIFF image
   .tiff
XBM bitmap image
   .xbm
JPEG image
   .jpg or .jpeg
PostScript file
   .ps
AIFF sound
   .aiff
AU sound
   .au
QuickTime movie
   .mov
MPEG movie
   .mpeg or .mpg

Make sure your intended audience has the necessary viewers. Most UNIX
workstations, for instance, cannot view QuickTime movies.

Troubleshooting

Avoid Overlapping Tags

Consider this snippet of HTML:

    <B>This is an example of <DFN>overlapping</B> HTML tags.</DFN>

The word ``overlapping'' is contained within both the <B> and <DFN> tags. How
does the browser format it? You won't know until you look, and different
browsers will likely react differently. In general, avoid overlapping tags.

Embed Anchors and Character Tags, But Nothing Else

It is acceptable to embed anchors within another HTML element:

    <H1><A HREF = "Destination.html">My heading</A></H1>

Do not embed a heading or another HTML element within an anchor:

    <A HREF = "Destination.html">
    <H1>My heading</H1>
    </A>

Although most browsers currently handle this example, it is forbidden by the
official HTML and HTML+ specifications, and will not work with future browsers.

Character tags modify the appearance of other tags:

    <UL><LI><B>A bold list item</B>
        <UL>
        <LI><I>An italic list item</I>
    </UL>

However, avoid embedding other types of HTML element tags. For example, it is
tempting to embed a heading within a list, in order to make the font size
larger:

    <UL><LI><H1>A large heading</H1>
        <UL>
        <LI><H2>Something slightly smaller</H2>
    </UL>

Although some browsers, such as NCSA Mosaic for the X Window System, format this
construct quite nicely, it is unpredictable (because it is undefined) what other
browsers will do. For compatibility with all browsers, avoid these kinds of
constructs.

What's the difference between embedding a <B> within a <LI> tag as opposed to
embedding a <H1> within a <LI>? This is again a question of SGML. The semantic
meaning of <H1> is that it's the main heading of a document and that it should
be followed by the content of the document.Thus it doesn't make sense to find a
<H1> within a list.

Character formatting tags also are generally not additive. You might expect that

    <B><I>some text</I></B>

would produce bold-italic text. On some browsers it does; other browsers
interpret only the innermost tag (here, the italics).

Check Your Links

When an <IMG> tag points at an image that does not exist, a dummy image is
substituted. When this happens, make sure that the referenced image does in fact
exist, that the hyperlink has the correct information in the URL, and that the
file permission is set appropriately (world-readable).

A Longer Example

Here is a longer example of an HTML document:

    <HEAD>
    <TITLE>A Longer Example</TITLE>
    </HEAD>
    <BODY>
    <H1>A Longer Example</H1>
    This is a simple HTML document. This is the first
    paragraph. <P>
    This is the second paragraph, which shows special effects.  This is a
    word in <I>italics</I>.  This is a word in <B>bold</B>.
    Here is an in-lined GIF image: <IMG SRC = "myimage.gif">.
    <P>
    This is the third paragraph, which demonstrates links.  Here is
    a hypertext link from the word <A HREF = "subdir/myfile.html">foo</A>
    to a document called "subdir/myfile.html". (If you
    try to follow this link, you will get an error screen.) <P>
    <H2>A second-level header</H2>
    Here is a section of text that should display as a
    fixed-width font: <P>
    <PRE>
        On the stiff twig up there
        Hunches a wet black rook
        Arranging and rearranging its feathers in the rain ...
    </PRE>
    This is a unordered list with two items: <P>
    <UL>
    <LI> cranberries
    <LI> blueberries
    </UL>
    This is the end of my example document. <P>
    <ADDRESS>Me ([e-mail])</ADDRESS>
    </BODY>

Click here to see the formatted version.

In addition to tags already discussed, this example also uses the <HEAD> ...
</HEAD> and <BODY> ... </BODY> tags, which separate the document into
introductory information about the document and the main text of the document.
These tags don't change the appearance of the formatted document at all, but are
useful for several purposes (for example, NCSA Mosaic for Macintosh 2.0, for
example, allows you to browse just the header portion of document before
deciding whether to download the rest), and it is recommended that you use these
tags.

For More Information

This guide is only an introduction to HTML and not a comprehensive reference.
Below are additional sources of information.

Fill-out Forms

One major feature not discussed here is fill-out forms, which allows users to
return information to the World Wide Web server. For information on fill-out
forms, look at this Fill-out Forms Overview

Style Guides

The following offer advice on how to write ``good'' HTML:

   Composing Good HTML
   CERN's style guide for online hypert

Other Introductory Documents

These cover similar information as this guide:

   How to Write HTML Files
   Introduction to HTML

Additional References

   The HTML Quick Reference Guide, which provides a comprehensive listing of
   HTML codes
   The official HTML specification
   A description of SGML, the Standard Generalized Markup Language
   Dan Connolly's HTML Design Notebook. Dan Connolly is one of the originators
   of HTML.


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