Best Practice to Create Dynamic URL's- With Username

Hi All, I am creating a social networking website. I want that every user should have there own profile page with a static URL like- http://www.abcnetwork/user/username Where username will be dynamic userid or something else. This is something very similar to www.youtube.com/user/kumargauravmail (this is my profile page). So what should be the best practice to create such DYNAMIC URL's OR what kind of methodology youtube is following? Thanks in Advance. Gaurav Kumar OSWebstudio.com