On some .NET driven sites URLs don't end with asp.net page names, like default.aspx, instead they use a pattern http://sitename.com or http://sitename.com/subdirectory/subdirectory. The site is mapped as sub directories off the root, ie. /tags, /users, /badges, the URLs would be /tags, /users, /badges respectively.
StackOverflow, to use a specific example, uses question URLs of the form http://stackoverflow.com/questions/1035251/how-do-get-clean-urls-like-stackoverflow. Which is great way to optimize the page for search engines.
Is this implemented using HTTP handlers? Is the GET request filtered based on path and the whole response is formed in the handler itself based on the question id? Anyone else care to speculate?