CSS

====CSS 2.1====
CSS level 2 revision 1, often referred to as "CSS 2.1", fixes errors in CSS&nbsp;2, removes poorly supported or not fully interoperable features and adds already implemented browser extensions to the specification. To comply with the W3C Process for standardizing technical specifications, CSS&nbsp;2.1 went back and forth between Working Draft status and Candidate Recommendation status for many years. CSS 2.1 first became a [https://www.w3.org/TR/2004/CR-CSS21-20040225/ Candidate Recommendation] on 25 February 2004, but it was reverted to a Working Draft on 13 June 2005 for further review. It returned to Candidate Recommendation on 19 July 2007 and then updated twice in 2009. However, because changes and clarifications were made, it again went back to Last Call Working Draft on 7 December 2010.

CSS 2.1 went to Proposed Recommendation on 12 April 2011.<ref>[[W3C]]:''[https://www.w3.org/TR/2011/PR-CSS2-20110412/ Cascading Style Sheets, level 2 revision 1] {{Webarchive|url=https://web.archive.org/web/20111109095352/https://www.w3.org/TR/2011/PR-CSS2-20110412/ |date=2011-11-09 }} CSS 2.1 specification (W3C Proposed Recommendation)''</ref> After being reviewed by the W3C Advisory Committee, it was finally published as a W3C Recommendation on 7 June 2011.<ref name="w3.org">W3C: [https://www.w3.org/2011/05/css-pr.html.en Cascading Style Sheets Standard Boasts Unprecedented Interoperability] {{Webarchive|url=https://web.archive.org/web/20110610221708/https://www.w3.org/2011/05/css-pr.html.en |date=2011-06-10 }}</ref>

CSS 2.1 was planned as the first and final revision of level 2—but low-priority work on CSS 2.2 began in 2015.