Google Doctype - Web Developers Wiki

Google released Doctype (HTML version), a wiki of the open web.

Google Doctype is an encyclopedia that can be edited by anyone who has a Google account and wants to keep it up-to-date or add new articles. The encyclopedia contains articles about web security, DOM manipulation, CSS, HTML best practices, references for HTML, DOM, CSS, complete with browser compatibility information. There's also previously-unreleased code used internally by Google that is now documented and available for anyone to use.

Google Doctype is 100% open.