The World Wide Web Consortium (W3C) Cascading Style Sheets (CSS) Working Group updated the Candidate Recommendation of “Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification.” CSS 2.1 is a style sheet language that allows authors and users to attach style (e.g., fonts and spacing) to structured documents (e.g., HTML documents and XML applications). CSS 2.1 corrects a few errors in CSS2 (the most important being a new definition of the height/width of absolutely positioned elements, more influence for HTML’s “style” attribute and a new calculation of the ‘clip’ property), and adds a few highly requested features which have already been widely implemented. But most of all CSS 2.1 represents a “snapshot” of CSS usage: it consists of all CSS features that are implemented interoperably. This draft incorporates errata resulting from implementation experience since the previous publication.