Best reference sites for HTML and JavaScript programming:
- W3C WebEd Wiki (this site has a self-teaching curriculum as well as reference material): HTML, CSS
- W3C Specifications: HTML4, HTML5 (working draft), CSS 2.1, DOM Tech Reports: levels 1-3
- ECMAScript: ECMAScript 5.1 (PDF), ECMAScript 3rd Ed., Annotated ES 5.1, HTML ES 3
- SitePoint: DOM JavaScript, HTML, CSS -- Search
- Mozilla Dev Center: DOM, JavaScript, JS Lang, AJAX, HTML, XHTML, SVG, Standards
- MSDN: HTML Elements, IE HTML Reference, CSS Attributes, IE CSS Reference, JavaScript Language, DOM
- Quirksmode: DOM Javascript, CSS, Compatibility
- ZVON: HTML, XML, CSS
- DevGuru - JavaScript, HTML, CSS, XML, Server-side
- Aptana - DOM0, DOM1+2, JavaScript Lang, Core, HTML, CSS
- GotAPI - DOM JavaScript, HTML, CSS, Server-side, Multimedia, XML
- SELFHTML French: DOM JavaScript, HTML, DHTML, CSS, XML, Server-side
- SELFHTML German: DOM JavaScript, HTML, DHTML, CSS, XML, Server-side
- Blooberry - HTML, CSS
- HTMLDog - HTML, CSS
- W3schools: DOM, JavaScript, HTML, CSS, XML, Multimedia, Server-side*
*There is some controversy over the quality and accuracy of the information in the tutorials offered by W3Schools. Not as many, however, take issue with the reference section.
Related questions, mostly the source of the above links: