A data format used to separate style from structure on Web pages.
Cascading style sheets (CSS) address many of the problems of old-style HTML. Some of the older tags, especially the notorious <FONT>, clutter Web page source code and make for inflexible sites. With CSS, style information can be centralized. This centralization leads to increased power and flexibility.
With cascading style sheets, designers are able to use tags to reference a style rather than describe it at each instance. Then, when a style needs to be changed, only the referenced declarations need to be changed, not all of the instances where it is used.
CSS information may be contained on each Web page, called from an external file, or both. For sites with many style declarations, the centralized method (external file) offers the most potential efficiency gains in terms of site management.
Flexible Layouts with CSS Positioning
A List Apart (November 15, 2002)
CSS Talking Points : Convincing Your Clients to go with Standards
A List Apart (July 6, 2001)
Effective Use of Style Sheets
useit.com Alertbox (July 1, 1997)