A User's Guide to Style Sheets

Handan Selamoglu
Microsoft Developer Network

June 25, 1996

Abstract

Style sheets, introduced in Microsoft Internet Explorer 3.0, are about to change the way people build and maintain their Web pages.

A style sheet works behind the scenes to give Web authors and designers more control and flexibility in their word- and design-smithing on the Web. Style sheets deliver some of the formatting features and control authors and designers have been enjoying for years in traditional desktop publishing--features that have been sorely missed on the Web. With style sheets, you can finally specify point sizes, page margins, and leading (spacing between lines). You can also create any number of formatting variations for a single HTML tag.

In addition to this new functionality, a style sheet provides a convenient service: It separates the formatting information from the actual content on your HTML pages, so it becomes much easier to design and revise your pages.

This document provides an introduction to style sheets and explains usage and syntax, as defined by the World Wide Web Consortium (W3C) and supported by Microsoft Internet Explorer 3.0.

Introduction
Browser support
Cascading style sheets

Three Ways to Add Style Sheets to Your Web Pages
   Basic syntax
   Linking to a style sheet
   Embedding a style block
   Using inline styles
   Mixing methods
   Additional options

Style Reference Guide
   Quick Reference
   Point Size
   Typeface
   Weight
   Style
   Leading (line height)
   Grouping font attributes
   Colors
   Special text effects
   Margins
   Alignment
   Indentation
   Background colors and images

Tips & Tricks
Designing for multiple browsers
Taking advantage of inheritance

Samples (coming soon!)

Introduction

A style sheet is a template that controls the formatting of HTML tags on your Web pages. If you use Microsoft Word, you will find the concept of style sheets very similar to Word templates: You can alter the appearance of a Word document by changing the formatting assigned to styles in your document. Similarly, you can alter the appearance of a Web page by changing the formatting assigned to HTML tags through a style sheet, and thus override the browser's default specification for those tags.

If you publish on the Web, you may want to take advantage of style sheets for three main reasons: additional formatting, better control, and easier customization. Specifically, style sheets allow you to:

Use leading, margins, indents, point sizes, and text background colors on your Web pages. Authors and designers take these formatting features for granted, but HTML does not support these directly through its standard set of tags.
Stop using awkward workarounds for basic formatting tasks (such as <BLOCKQUOTE> for margins).
Change the formatting of individual Web pages or your entire site without touching every single line in your HTML files.
Reduce the clutter of tags on your HTML pages (because you don't need to turn tags on and off to change the design of a single element).
Define design variations through classes (for example, if you need five different paragraph styles, you can specify five classes for the <P> tag, e.g., P.normal, P.indented, P.underlined, P.red, P.dblspaced).

Browser support

Style sheets are fairly new to the Web. Internet Explorer 3.0 is the first Web browser to support style sheets. The Internet Explorer 3.0 implementation of style sheets is based on the W3C working draft called "Cascading Style Sheets, Level 1" (dated May 1996, http://www.w3.org/pub/WWW/TR/WD-css1.html). Spyglass and Netscape have also indicated that they will support style sheets in future versions of their browsers. Browsers that don't support style sheets display the pages using the browser's default specs instead. (See "Tips & Tricks" for instructions on how to set up your style sheets so they don't cause problems in other browsers.)

Cascading style sheets

The W3C draft refers to "cascading style sheets" because you can use multiple styles to control the appearance of your page, and the browser follows rules (a "cascading order") to determine precedence and to resolve conflicts. For example, the Web author can use linked, embedded, and inline styles (described below) in one document, and Web readers can have their own personal style sheets. If the linked style sheet defines a heading tag as blue, the top-of-page style sheet defines it as red, and the reader wants to see purple, the browser has to decide what to display. Cascading rules are discussed in "Mixing Methods" later in this article.

Three Ways to Add Styles to Your Web Pages

You can use style sheets in three ways, depending on your design needs:

By linking to a style sheet from your HTML file. This method allows you to change the appearance of multiple Web pages by tweaking a single file.
By embedding a style sheet in your HTML file. This method allows you to change the appearance of a single Web page by tweaking a few lines.
By adding inline styles to your HTML file. This gives you a quick way to change the appearance of a single tag, a group of tags, or a block of information on your page.

You can use one, two, or all three of these methods on your pages. The sections below discuss each method and syntax in detail. For detailed information, see the W3C documents: HTML3 and Style Sheets

and Cascading Style Sheets, Level 1

Basic Syntax

Both linked and embedded style sheets include one or more style definitions. (The inline style syntax is somewhat different, as we'll discuss later.) A style definition consists of an HTML tag (any tag), followed by a listing of properties for that tag within curly braces. Each property is identified by the property name, followed by a colon and the property value. Multiple properties are separated by semicolons. For example, the following style definition assigns the <H1> tag a specific font size (15 points) and font weight (boldface):

  H1 {font-size: 15pt;
      font-weight: bold}

You can thus create style definitions for any number of HTML tags and either place them in a separate file or embed them directly within your Web pages. For a list of properties, see the "Style Reference Guide" section below.

Linking to a style sheet

To link to an external style sheet, you simply create a file with your style definitions (as explained below for embedded styles), save it with a .CSS file extension, and link to it from your Web page. This way, you can use the same style sheet for any number of pages on your site.

For example, if your style sheet is called MYSTYLES.CSS and is located at the address http://www.company.com/mystyles.css, you would add the following to your Web page, within the <HEAD> tag:

<HEAD>
<TITLE>Title of article</TITLE>
<LINK REL=STYLESHEET HREF="http://www.company.com/mystyles.css" TYPE="text/css">
</HEAD>

Please note! Internet Explorer 3.0 Beta 1 does not automatically register the Internet Media (MIME) type for style sheets, so if you're using a linked style sheet, the server administrator on the user's site must register the "text/css" type on the server. This will be fixed in a future release of the Internet Explorer 3.0. Until then, you might consider using embedded style sheets instead.

Embedding a STYLE block

To embed a style sheet, you add a <STYLE> </STYLE> block at the top of your document, between the <HTML> and <BODY> tags. This allows you to change the appearance of a single Web page. The <STYLE> tag has one parameter, TYPE, which specifies the Internet Media type as "text/css" (allowing browsers that do not support this type to ignore style sheets). The <STYLE> tag is followed by any number of style definitions and terminated with the </STYLE> tag.

The following example specifies styles for the <BODY>, <H1>, <H2>, and <P> tags:

<HTML>
<STYLE TYPE="text/css">
<!--
  BODY {font: 10pt "Arial"};
  H1 {font: 15pt/17pt "Arial";
      font-weight: bold;
      color: maroon}
  H2 {font: 13pt/15pt "Arial"; 
      font-weight: bold;
      color: blue}
  P  {font: 10pt/12pt "Arial";
      color: black}
-->
</STYLE>
<BODY>
...
</BODY>
</HTML>

See the "Tips & Tricks" section to find out why I've added HTML comments () within the style block.

Using inline styles

If you want to take advantage of point sizes, indentation, or other styles in only a few sections of your Web page, you can use inline styles.

Inline style definitions affect individual occurrences of a tag. These are embedded within the tag itself using the STYLE parameter. The following HTML code indents a specific <P> tag:

<P STYLE="margin-left: 0.5in; margin-right: 0.5in">
This line will be indented on the left and right.
<P>
This line will receive no indentation.

Here's the result (this display requires Internet Explorer 3.0):

This line will be indented on the left and right.

This line will receive no indentation.

If the inline style conflicts with an embedded or linked style, the inline style overrides for that particular occurrence. For example, if the line above appears on a Web page that defines <P> with 1-inch margins through a linked style sheet, all paragraphs on the Web page will get 1-inch margins except for the <P> above, which will get 0.5-inch margins.

If you want to change the appearance of an entire section, you can use the <SPAN> tag to define styles globally for that section. The following example changes the color and point size of a block of text by using the <SPAN> tag (this has the same affect as assigning these styles separately for the <P>, <UL>, and <LI> tags):

<SPAN STYLE="font-size: 14pt; color: green">
<P>
The style specification affects everything on this page until the SPAN close tag.
<UL>
<LI>This is green and 14 pt.
<LI>So is this.
</UL>
</SPAN>

Result (requires Internet Explorer 3.0):

The style specification affects everything on this page until the SPAN close tag.

This is green and 14 pt.
So is this.

The following example uses the <SPAN> tag for a block of text, but overrides it for a specific <LI> tag:

<SPAN STYLE="font-size: 14pt; color: green">
<P>
The style specification affects everything on this page until the SPAN close tag, except for the second list item.
<UL>
<LI>This is green and 14 pt.
<LI STYLE="color: blue">This is blue and 14 pt.
</UL>
</SPAN>

Result (requires Internet Explorer 3.0):

The style specification affects everything on this page until the SPAN close tag, except for the second list item.

This is green and 14 pt.
This is blue and 14 pt.

Inline styles are simple to use if you're focusing on a few tags or sections on your Web page (for example, you're highlighting a heading or indenting an abstract). However, inline styles clutter up your HTML pages, and revisions require more detailed attention (because you have to change multiple lines scattered throughout your HTML file). If you want to make global changes to one or more Web pages, you'll find that using a centralized STYLE block (either linked or embedded) is easier and more efficient.

Mixing methods

If you're just starting out with style sheets, it's probably a good idea to stick to one method that best addresses your needs. However, you may have complicated requirements that can be met only by using two or all three methods. Here are some scenarios:

You may wish to store your styles in separate style sheets (one storing the basic page layout for simple documents, and others customizing the layout for different types of documents), and link to multiple .CSS files at the top of your page. (Please note: Links to multiple style sheets are not supported in Internet Explorer 3.0 Beta 1.)
You may wish to link to your company-wide style sheet for consistency, but provide style variations (through classes) with an embedded style sheet.
You may wish to link to your company-wide style sheet, but override several specific elements using inline styles.
In the future, readers will be able to create their own style sheets to view your documents. When readers' style sheets are supported, you may wish to use style sheets to provide formatting that is essential to your page design, and let readers adjust the point size, leading, and typeface to suit their personal preferences.

So what happens if you use multiple style sheets that have conflicting style information? That's where the "cascading order" comes into play. In general, the author's style sheets override the reader's style sheet, which in turn overrides the browser's default values. If the author uses all three methods listed above, the inline styles take precedence over the embedded <STYLE> block, which overrides the linked style sheet. (Please note: In Internet Explorer 3.0 Beta 1, the linked style sheet retains precedence over the embedded <STYLE> block.)

Additional options

Simplification through grouping

If you want to assign the same formatting to multiple tags, for example:

  H1 {font-size: 15pt;
      font-weight: bold;
      color: maroon}
  H2 {font-size: 15pt;
      font-weight: bold;
      color: maroon}
  H3 {font-size: 15pt;
      font-weight: bold;
      color: maroon}

you can group them thus:

  H1 H2 H3 {font-size: 15pt;
            font-weight: bold;
            color: maroon}

You can also group formatting specifications. Take:

  H1 {font-size: 15pt;
      line-height: 17pt;
      font-weight: bold;
      font-family: "Arial";
      font-style: normal}

and simplify it this way:

  H1 {font: 15pt/17pt bold "Arial" normal}

(See the "Style Reference Guide" section below for more information on grouping font specs.)

Variations through classes

Use classes to create variations for a single HTML tag. For example, if you'd like to use three colors for your H1 headings (say, depending on context), you'd define three classes in your STYLE tag:

<STYLE>
  H1.red {font: 15pt/17pt;
          color: red}
  H1.green {font: 15pt/17pt;
          color: green}
  H1.blue {font: 15pt/17pt;
          color: blue}
</STYLE>

and use them as follows on your Web page:

<H1 CLASS=red>This is the red heading</H1>
...
<H1 CLASS=blue>This is the blue heading</H1>
...
<H1 CLASS=green>You get the picture...</H1>

Links

The style sheet implementation also allows you to customize the appearance of links (text that the user clicks to jump to another page) by assigning two predefined classes to the <A> (anchor) tag:

A:link represents a link that hasn't been visited (clicked).
A:visited represents a link that the user has already clicked.

You can set any font or text formatting properties on these anchor classes, including color, font-size, font-weight, and text-decoration. For example, to assign specific colors to the three types of links, you can specify:

  A:link {color: red}
  A:visited {color: blue}

Setting text-decoration to "none" allows you to remove the underlining from the link text:

  A:visited {color: blue; text-decoration: none}

Notes: Internet Explorer 3.0 Beta 1 does not support the A:active class, which represents a link that is currently being visited (for example, if your Web page consists of two frames--a contents frame and a viewer frame--and you click a link in the contents frame, the link will be "active" while you're viewing that article). In Internet Explorer 3.0 Beta 1, you'll also find that if you set a property on A:link, visited links inherit that property.

Comments

You can add comments to your style sheet to explain your design decisions. Comments can appear on any line in the style specification, between the characters /* and */--for example:

  H1 {font: 20pt/22pt bold; color=#00FF00} /* Green for heading 1 */

Style Reference Guide

This section provides a list of properties you can use in your style specifications with Internet Explorer 3.0 Beta 1. See the W3C "Cascading Style Sheets, Level 1" working draft for a complete list of the standard properties.

Note that Internet Explorer 3.0 does not currently support all of the attribute types and values documented in the W3C working draft. In the sections below, we've noted some of the differences in supported values.

Note: Internet Explorer 3.0 is currently available only as a beta version, so you may find that some of the style properties listed in this section do not work as documented. If you encounter any problems, try switching the properties around. For example, if you assigned two properties, font-weight and color (in that order), to the <H1> tag and encounter problems, try switching the order.

Quick reference

Attribute Description Values Example

font-size Sets size of text. points (pt)
inches (in)
centimeters (cm)
pixels (px) {font-size: 12pt}

font-family Sets typeface. typeface name
font family name {font-family: courier}

font-weight Sets thickness of type. normal
bold {font-weight: bold}

font-style Italicizes text. italic {font-style: italic}

line-height Sets leading (line height). points (pt)
inches (in)
centimeters (cm)
pixels (px) {line-height: 24pt}

color Sets color of text. color-name
RGB triplet {color: blue}

text-decoration Underlines or otherwise highlights text. none
underline
italic
line-through {text-decoration: underline}

margin-left Sets distance from left edge of page. points (pt)
inches (in)
centimeters (cm)
pixels (px) {margin-left: 1in}

margin-right Sets distance from right edge of page. points (pt)
inches (in)
centimeters (cm)
pixels (px) {margin-right: 1in}

text-align Sets justification. left
center
right {text-align: right}

text-indent Sets distance from left margin. points (pt)
inches (in)
centimeters (cm)
pixels (px) {text-indent: 0.5in}

background Sets background images or colors. URL,
color-name
RGB triplet {background: #33CC00}

Point size

The font-size attribute sets the size of the text in points, inches, centimeters, or pixels. For example:

{font-size: 12pt}
{font-size: 1in}
{font-size: 5cm}
{font-size: 24px}

Typeface

The font-family attribute sets the typeface used for text. You can specify a single typeface:

{font-family: Arial}

or alternatives, separated by commas:

{font-family: Arial, Helvetica}

The line above ensures that Helvetica is used on systems that don't support Arial. You can also indicate a generic family name (serif, sans-serif, or monospace) as a last alternative:

{font-family: Arial, Helvetica, sans-serif}

If you're referencing a typeface that consists of multiple words, use quotation marks:

{font-family: "Courier New"}

Weight

The font-weight attribute sets the thickness of type. Internet Explorer supports two weights: normal and bold:

{font-weight: normal}
{font-weight: bold}

Style

The font-style attribute sets italic text:

{font-style: italic}

(Note that the W3C working draft also references small caps, oblique, and a few other styles, which are not currently supported by Internet Explorer.)

Leading (line height)

The line-height attribute sets "leading" (the distance between the baselines of two lines). You can specify leading in points, inches, centimeters, or pixels. For example:

{line-height: 20pt}

(Note that in Internet Explorer 3.0 beta, the spacing is added before lines, not after lines.)

Grouping font attributes

The attributes listed above are ones that you will probably use frequently in your style sheets, so the W3C specifies (and Internet Explorer supports) a shortcut notation. Instead of setting the attributes separately, you can combine them into one attribute called font.

Thus, instead of:

 P {font-family: Times, serif;
    font-size: 12pt;
    line-height: 20pt;
    font-weight: bold;
    font-style: italic}

you can simply use:

 P {font: "Times, serif" 12pt/20pt bold italic}

Colors

The color attribute sets the type to a named color or RGB value. You can use the 16 named colors or red-green-blue (RGB) color values:

{color: teal}
{color: #33CC00}

Named colors consist of the following:

black silver gray white

maroon red purple fuchsia

green lime olive yellow

navy blue teal aqua

For a complete color chart with hexidecimal RGB values, see the Internet Explorer Palette.

Special text effects

The text-decoration attribute allows you to use underlining and strike-through for text. The supported values are underline, line-through, none, and italic.

{text-decoration: underline}
{text-decoration: line-through}

(The W3C working draft also references overline and blink, which are not currently supported by Internet Explorer.) To see an example of how you can use text-decoration to turn underlining off for links, see "Links" above.

Margins

The margin-left and margin-right attributes set the side margins for a tag. You can specify the margins in points, inches, centimeters, or pixels. For example:

BODY {margin-left: 0.5in;
      margin-right: 0.5in}

sets half-inch margins on either side of your page.

Alignment

The text-align attribute lets you left-justify, center, or right-justify HTML elements:

{text-align: left}
{text-align: center}
{text-align: right}

Indentation

In addition to using margins, you can also set additional indentation for sections of your page using the text-indent attribute. Again, you can specify indentation in points, inches, centimeters, or pixels. For example:

H2 {text-indent: 0.5cm}

causes your level-2 headings to be indented 0.5 centimeters from the left margin.

Background colors and images

You can use the background attribute to highlight sections of your page by setting a background color or background image. To set a color, you specify a named color (see the color attribute above) or use an RGB color value:

{background: red}
{background: #6633FF}

To place an image, you specify the URL in parentheses:

{background: URL(http://www.microsoft.com/intdev/boxes.gif)}

Tips & Tricks

Designing for multiple browsers

If you're using embedded styles, you need to make sure that your style definitions do not get displayed as regular text in browsers (such as Netscape) that don't support style sheets. (Netscape will ignore the <STYLE> and </STYLE> tags, but will interpret the style definitions in between these as regular text, because they are not enclosed in angle brackets. To fix this, embed your style block within a comment, as follows:

<STYLE>
<!--
  BODY {font: 10pt "Arial"};
  H1 {font: 15pt/17pt "Arial";
      font-weight: bold;
      color: maroon}
  H2 {font: 13pt/15pt "Arial"; 
      font-weight: bold;
      color: blue}
  P  {font: 10pt/12pt "Arial";
      color: black}
-->
</STYLE>

Taking advantage of inheritance

The HTML tags on your page follow a chain of inheritance. The top-level (parent) tag is <HTML> followed by <BODY>. If you assign styles to the <BODY> tag, your tables, lists, paragraphs, and all other lower-level HTML elements will inherit from it. Thus, to set the global layout and formatting for your entire page, you can simply assign the appropriate properties to the <BODY> tag. For example:

  BODY {font: 10pt/11pt Arial, Helvetica, sans-serif; 
        background: url(clouds.gif);
        margin-left: 0.5in;
        margin-right: 0.5in}

sets the default font, leading, background image, and margins for your entire page. If you need to override the default for specific elements within your page (for example, you need tables indented further or your abstract paragraph in smaller type), you can add style specifications for those tags in your style sheet. The tags you haven't set in your style sheet will inherit from their parent tags or from <BODY>.

Samples

Check back soon for additional samples of Web pages designed with style sheets.

Attribute	Description	Values	Example
font-size	Sets size of text.	points (pt) inches (in) centimeters (cm) pixels (px)	{font-size: 12pt}
font-family	Sets typeface.	typeface name font family name	{font-family: courier}
font-weight	Sets thickness of type.	normal bold	{font-weight: bold}
font-style	Italicizes text.	italic	{font-style: italic}
line-height	Sets leading (line height).	points (pt) inches (in) centimeters (cm) pixels (px)	{line-height: 24pt}
color	Sets color of text.	color-name RGB triplet	{color: blue}
text-decoration	Underlines or otherwise highlights text.	none underline italic line-through	{text-decoration: underline}
margin-left	Sets distance from left edge of page.	points (pt) inches (in) centimeters (cm) pixels (px)	{margin-left: 1in}
margin-right	Sets distance from right edge of page.	points (pt) inches (in) centimeters (cm) pixels (px)	{margin-right: 1in}
text-align	Sets justification.	left center right	{text-align: right}
text-indent	Sets distance from left margin.	points (pt) inches (in) centimeters (cm) pixels (px)	{text-indent: 0.5in}
background	Sets background images or colors.	URL, color-name RGB triplet	{background: #33CC00}

black	silver	gray	white
maroon	red	purple	fuchsia
green	lime	olive	yellow
navy	blue	teal	aqua