CSS: Cascading Style Sheets

Goal: The W3C style sheet language for XML/HTML documents
Platform independence, document and site maintenance, adaptability to network performances

From CSS1 to CSS2 and CSS3

CSS 1: basic styles : color, font, character size, margin, ...
CSS2: higher level formatting features (placement, dynamic font, tables, element numbering) and media-specific style sheets (print, audio), ...
CSS3: modular specifications, new features: multiple columns...