Stylesheets are the way publishing professionals manage the overall “look” of their publications—backgrounds, fonts, colors, and so on—from a single page to huge collections of documents. Most desktop publishing software supports stylesheets, as do popular word processors, so using stylesheets for HTML documents is obvious.
For the most part, HTML focuses on content over style. Authors are encouraged to worry about providing high-quality information and leave it to the browser to worry about presentation. We strongly urge you to adopt this philosophy in your documents—don’t mistake style for substance.
However, presentation is for the benefit of the reader, and even the original designers of HTML understand the interplay between style and readability—for example, through the physical style and header tags. Stylesheets extend that presentation with several additional effects, including colors, a wider selection of fonts, and even sounds so that users can better distinguish elements of your document. But most importantly, stylesheets let you control the presentation attributes for all the tags in a document—for a single document or a collection of many documents—from a single master.
In early 1996, the World Wide Web Consortium (W3C) put together a draft proposal defining Cascading Style Sheets (CSS) for HTML. This draft proposal quickly matured into a recommended standard. In mid-1998, the W3C extended the original specification to create CSS2, which ...