AlsacréationS : Alsacréations est une communauté dédiée à l'apprentissage des standards web (W3C, HTML, XHTML, CSS) ainsi qu'à l'accessibilité numérique
Email Standards Project : The Email Standards Project is about working with email client developers and the design community to improve web standards support and accessibility ...
&what: Discover Unicode & HTML Character Entities : amp-what is a quick, interactive reference of 14,500 HTML character entities* and common Unicode characters, 8859-1 characters, quotation marks, punct...
CSS Reference : Learn by example: cssreference.io is a free visual guide to CSS. It features the most popular properties, and explains them with illustrated and anima...
This site provides a collection of schemas that webmasters can use to markup HTML pages in ways recognized by major search providers, and that can also be used for structured data interoperability (e.g. in JSON).
Codelabs management & hosting tools : Codelabs are interactive instructional tutorials, which can be authored in Google Docs using some simple formatting conventions. You can also author c...
StyleDocco : StyleDocco generates documentation and style guide documents from your stylesheets.
Docusaurus : Easy to Maintain Open Source Documentation Websites
Mobile HTML5 compatibility : HTML5 compatibility on mobile and tablet browsers with testing on real devices
TLDR pages : The TLDR pages are a community effort to simplify the beloved man pages with practical examples.