- HTML Developer Guide at MDN
- The MDN is the Mozilla Developer’s Network, maintained by the Mozilla Foundation (creators of Firefox, among other things). Their network contains tutorials, examples, and references for lots of web technologies, and they’re all pretty good.
- HTML Web Platform Docs
- The WebPlatform.org website is jointly maintained by the W3C and a coalition of industry stewards (Adobe, Apple, Facebook, Google, HP, Intel, Microsoft, Mozilla, Nokia, and Opera). Its aim is to provide easy-to-read tutorials, articles, and reference material for web developers across the world. The site is a work in progress, but the section on HTML is fairly complete, and very good.
- Web Style Guide
- This book (now in its third edition) is a guide to creating websites that are usable, accessible, and SEO-friendly. It focuses on design concepts, not on coding techniques; chapters are dedicated to such topics as site structure, page design, or editorial style. In my opinion, everyone who creates web content should read it.
- HTML5 Doctor
- As the name suggests, the site is devoted to HTML5 semantics, with an emphasis on using HTML5 tags immediately (sometimes before the standards are finalized). So, the team of authors make it a point to stay up-to-date on the latest W3C working drafts and WHATWG living standards. The site also maintains a very good index of HTML elements, often with links to articles on usage (“our prognosis”) that are updated if the specifications change.
- Dive Into HTML5
- HTML at W3Schools
I’d like to thank Ben Drasin, who pointed out some issues with the section on attribute minimization.