HTML
- HTML/XTML in one page
- HTML5: The Evolution of Web Standards by James Sugrue
- (X)HTML Elements and Attributes
- Doctype Declarations (DTDs)
- XHTML Character Entity Reference
- GoSquared HTML Help Sheet
CSS
- CSS in one page
- CSS Properties and Values
- All CSS Properties Listed Alphabetically
- CSS Shorthand Guide
- GoSquared CSS Help Sheet
PHP
- PHP Basics Quick Reference Sheet
- PHP Cheat Sheet
- PHP Security Cheat Sheet
- PHP Variable and Array Tests
- GoSquared PHP Help Sheet
JavaScript
XML & Unicode