Cascading Style Sheets (otherwise known as CSS) is a simple mechanism for adding style (e.g.fonts, colors, spacing) to Web documents.
CSS is formally described in two specifications from W3C: CSS1 and CSS2.
CSS1 was issued in December 1996 and describes a simple formatting model mostly for screen-based presentations. It has around 50 properties (for example color and font-size).
CSS2 was finalized in May 1998 and builds on CSS1. CSS2 includes all CSS1 properties and adds around 70 of its own, such as properties to describe aural presentations and page breaks.
If you would like to read the CSS specifications themselves, you can find them from:
Cascading Style Sheets Tutorials, books, mailing lists for users, etc. can be found on the “learning CSS” page.
For background information on style sheets, see the Web style sheets page. Discussions about CSS are carried out on the (archived) email@example.com mailing list (and sometimes on the CSSblog) and on comp.infosystems.www.authoring.stylesheets.