Specifications
- WHATWG HTML Living Standard - The official HTML specification
- W3C HTML 5.2 - W3C Recommendation
Validators
- W3C Markup Validator - Check HTML validity
- Nu HTML Checker - Modern HTML validator
References
- MDN HTML Documentation - Comprehensive HTML reference
- Can I Use - Browser compatibility tables
Accessibility
- ARIA Authoring Practices Guide - WAI-ARIA patterns
- WAVE Web Accessibility Evaluator - Test page accessibility
- The A11Y Project - Accessibility resources