How to execute this URL mentioned below

Hi Expert viewers,

I have some difficulty how to execute the following url www.myspace.com/astahsildar as www.myspace.com is doing. The www.myspace.com url is followed by the myspace unique name, if any person type his/her myspace name his profile is shown.I am the registered user of www.myspace.com and my myspace url is
http://www.myspace.com/astahasildar
The similar thing I want to implement in my project which is SNS site.
Presently I am using Struts1.2, jdk1.5, JSP2.0,JSTL, EJB2.0 .

I was trying to do some settings in web.xml but i could not get any solution.Please help me to find the solution.
I will be grateful to you.

Regards,
Ashish