PHP

php.net PHP Usage Original PHP announcement

Head First HTML and CSS

The book on Safari Downloads for the examples in the book

HTML

URLs at whatwg.org Live Diagram of Content Categories Optional Tags

CSS

Selectors, Specificity, and the Cascade CSS 2.1 REC Full Property Table CSS: The Definitive Guide, 3rd ed. by Eric Meyer; on Safari Descriptions of all CSS specifications Default style sheet for HTML4 CSS Zen Garden CSS Color Module Level 3 CSS reference at sitepoint.com css3playground.com

Chrome

Chrome Developer Tools

In the news

Notehall Founder and UA Alum Sean Conway to Deliver Keynote Address at IdeaFunding 2013 SEC filing cracks the egg on Chegg's Notehall purchase Healthcare.gov: Code Developed by the People and for the People, Released Back to the People HealthCare.gov for Developers

Misc

Quirks Mode and Standards Mode, on MDN Hacking with a Hacker, re buttonhole trap The Smoke-Filled Room 456 Berea ^ST bricss.net—Bite-Sized CSS & HTML Nuggets