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TML is a language designed to define the structure of a document. As it evolved, tags were added

to HTML to handle formatting, but these were difficult to work with, difficult to edit, and added

considerably to the page’s file size. Cascading Style Sheets (CSS) was introduced both to solve all of

these issues as well add additional formatting controls. With CSS, you can change your text properties,

control the spacing between elements on your page, draw borders, add images, and much more. You

can use CSS to format any Web page, regardless of the version of HTML or XHTML you are using.

Introduction to CSS

Writing CSS

Like HTML, CSS documents are plain text and can be

written in any text editor. Modern HTML editors include

support for CSS as well, so the editor in which you are

writing your HTML should also work for your CSS.

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CSS Syntax

The syntax of CSS is quite a bit different from HTML. CSS documents are made up of

a series of rules. Each rule includes a selector and a declaration. Selectors are case-

sensitive, whereas the values and properties that make up declarations are not. Like

HTML, CSS is whitespace-insensitive.

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Selectors

Selectors define the parts of the HTML document to which the rules

will apply. Selectors can be HTML elements, or they can correspond to

the values of ID or class attributes within HTML. More complex

selectors allow you to apply rules to elements based on their position

relative to other elements.