- http://www.zvon.org/xxl/xhtmlReference/Output/comparison.html compares Strict and Transitional XHTML
- http://www.w3schools.com/ is a great web site for learning different web technologies
- http://www.quirksmode.org/dom/compatibility.html covers W3C DOM compatibility among different browsers and platforms
- http://www.w3schools.com/browsers/browsers_stats.asp provides up to date browser usage statistics
- http://nexgenmedia.net/evang/iemozguide/ provides migration guide from Internet Explorer to Mozilla
- http://www.w3.org/QA/Tools/#validators provides links for W3C (X)HTML/CSS validators.