Start with XHTML, Javascript, CSS and then go to PHP,RubyOnRails, Python or C#
My advice is to go to PHP because there is a ton of scripts for it and you can run websites without any additional costs(shared server). When you accustom to PHP you can go to C# and develop in ASP.net if you need some business grade webiste. You just have to start with something and when you become proficient just upgrade your knowledge.
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How To Become A Hacker
Of course Python is also great(Google uses it) so you can also take Zope/Plone:
Better Web Application Framework
There are tons of frameworks/languages and it all depends on your choice.
Here's what is possible with ASP.net(C#):
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