Why can't I change my website/facebook profile on Facebook?

[Somebody you may know.]

All my friends have added their facebook profiles on their contact information, and I'm the only one left.
If i try to add the website e.g. http://www.facebook.com/JonStewart and later try to click on the hyperlinked page, it says "Page Not Found".
Here's a picture of what I'm talking about if you aren't getting my question
http://s203.photobucket.com/albums/aa238...059gj4.jpg

Help please, I want to add my website.

[Undefined.]

Account tab -> account settings -> username -> now add your username and press ok, or whatever it is...
now you should have your facebook profile name in a matter of seconds, minutes or hours