www.w3schools.com

At W3Schools you will find all the Web-building tutorials you need, from basic HTML and XHTML to advanced XML, SQL, Database, Multimedia and WAP.

www.tizag.com

Syntax descriptions for PHP, HTML and CSS. Easy to use and understand. Also tutorials on the variuos languages.

metroui.org

Metro UI CSS - The front-end framework for developing projects on the web in Windows Metro Style Metro UI CSS developed with the advice of Microsoft to build the user interface ...