WebPlatform – A Huge Documentation For Web Technologies
WebPlatform is an open community, backed by the Internet giants, for documenting the web technologies.
The website aims to provide accurate, up-to-date and comprehensive references + tutorials for every part of client-side development and design, with quirks and bugs revealed and explained.
Besides this content, there is also a Q&A part where anyone can ask web design/dev-related questions to an active community to get answers.
For the web design/dev community that grew with W3Schools, WebPlatform is another must-bookmark.