Domain.com/yourname redirects

I was looking around the web, and i saw that on a few sites, (ex. Xanga) if you type in your account name or something after the domain ex. xanga.com/yourname , it would redirect you to xanga.com/home.aspx?user=yourname

i was wondering if anyone knows how they achieved this. And if it has something to do with the server-side language(in my case, asp)

Thanks for any help,
-Naaman