Comment by Kleo Petrov on "Best advanced resources to learn HTML and CSS?"

Web Fundamentals by Google - The best place for advanced topics on Web Optimization, Animations, Responsive Design and UI, Security, User Experience, HTML5 APIs, etc.

The content is separated in several sections:

Shows - Google's web series like Totally Tooling Tips, HTTP 203, Supercharged, New In Chrome, etc.
Tools - Google's products we use everyday explained
Showcase - deep look at sites and web apps that have achieved success and learn from their mistakes, discoveries and technical advancements

HTML5Rocks - Another great source of HTML and CSS knowledge with topics ranging from Mobile to Optimization.

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