W3C Invites Implementations of CSS Containment Module Level 1

The CSS Working Group invites implementations of CSS Containment Module Level 1 Candidate Recommendation. This CSS module describes the 'contain' property, which indicates that the element’s subtree is independent of the rest of the page. This enables heavy optimizations by user agents when used well. CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, in speech, etc.