This is a page from the Cascading Style Sheets Working Group Blog. Some other places to find information are the “current work” page, the www-style mailing list, the Future of CSS syndicator, and the issue list on Github.
Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
::marker
(Issue #3809):picture-in-picture
and :fullscreen
to Selectors 4 (Issue #3796):picture-in-picture
needs a permanent location that Selectors 4 can reference.::marker
to interface CSSPseudoElement (Issue #3769)::marker
(Issue #3499)