How can I use LaTeX to build my website?

You could also look at Pandoc, which can be used as follows:

pandoc -r latex -w html -o outfile.html infile.tex

This will generate the HTML for you. You will have to specify your own stylesheets, however. Also, Pandoc only supports a subset of LaTeX.

LaTeX2HTML is a powerful TeX compiler to directly render a TeX document into HTML.

While installation of LaTeX2HTML involves several intricate steps, it is not impossible. Upon compilation, all necessary pages with the corresponding CSS is also created. Note, that the look of your document on the browser is only as good as you have developed it on TeX.

LaTeX2HTML is by far the best way to put your heavily loaded scientific and mathematical content on the web.

I agree with what was already said: you won't get the flexibility of manually playing with css, jquery/ajax, etc. However, as far as structured/markup languages are concerned, you may find the following two projects interesting:

• AsciiDoc: I used it after having tried reST (though now I'm more and more versed into Markdown); it has html5/tex backend, and can be used for website management.
• plasTeX: I used it for creating a tutorial with html output; it is driven by Python and has support for a templates and themes.

However, note that in general stylesheet as well as layout are specified outside of the core document.