You need to learn two generic type of languages, one for client scripting which is evaluated locally on your computer and the other the server side scripting which is evaluated[processed] on the server side.
Clientside: javascript,vbscript
(mostly for IIS),jscript and the most recommended ECMA script
Server side:ASP, ASP.Net -->Mostly IIS servers
JSP -->Java Server Pages for Apache,WebLogic and Sun Servers
PHP -->Open source, both Unix and windows
Best advice I can give is: Please go to: http://www.w3c.org There is no point in learning by heart, it is more like learning by doing.