This used to be a mirror that updated and built the CSS Working Group's Editor Draft specifications, as a stopgap measure since the canonical server for the Editor Drafts (drafts.csswg.org) was regularly down. However, since September 2022 the setup for this mirror is being used for a new semi-official mirror at https://w3c.github.io/csswg-drafts. Please go there instead.
This site is still used to test changes to the mirror setup in the andreubotella/csswg-auto-build GitHub repo, and you can check out that build output in https://andreubotella.com/csswg-auto-build/test/. But all links to the specs now redirect to the w3c.github.io/csswg-drafts mirror.
TLDR: Go to https://w3c.github.io/csswg-drafts instead. Thanks!