W3C
The world wide web consortium (w3c) is an international consortium where member organizations, a full-time staff, and the public work together to develop web standards. w3c primarily pursues its mission through the creation of web standards and guidelines designed to ensure long-term growth for the web. over 400 organizations are members of the consortium. w3c is jointly run by the mit pc science and artificial intelligence laboratory (mit csail) in the usa, the european research consortium for informatics and mathematics (ercim) headquartered in france, keio university in japan, and has additional offices worldwide.
http://www.w3.org/
XHTML
XHTML
http://www.w3.org/tr/xhtml1
PHP
PHP
http://www.php.net/
JAVA Script
Javascript.com is your source for all things javascript, including tutorials, free java scripts, downloads, tools, javascript source code and other scripting resources.
http://www.javascript.com/
CSS
W3c's overview of web style sheets: css.
http://www.w3.org/style/css
ASP.NET
Microsoft portal site for the asp.net development community. download visual web developer, post to the forums, read asp.net blogs and learn about asp.net.
http://www.asp.net/