https://www.cssui.dev/
CSSUI - Pure CSS interactive components
CSSUI is a collection of interactive user interface components realized in pure CSS.
pure csscssuiinteractivecomponents
https://lists.w3.org/Archives/Public/public-html-bugzilla/2011Aug/2009.html
[Bug 13613] Add normative reference to [CSSUI] and [SELECTORS]. from bugzilla@jessica.w3.org on...