Lol, even the extensions in ASP.NET that don't seem like HTML are HTML; they're just created by the Gods at Microsoft and Compiled to pump out.
Web Parts haven't even been matched by Yahoo or Google, although they have obviously tried with their 'Customisable' Sites. With ASP.NET - you can get it with a few lines of Code!
If you want to use something other than HTML - make your own IIS or Appache - make your own Browser - and write your own Handlers, then everybody with that Browser will be able to view your site :P Haha, but its probably not worth the bother. HTML is the most ingenious language available, so powerful yet so simple.
A Knight is sworn to Honour. His heart knows only Virtue. His blade defends the helpless. His might upholds the Weak. His word speaks only truth. His wrath undoes the Wicked.