I want to know how is possible for the admins to find out who is who by the time the IP always every next reconnect is changing..

huh? English please

How do the admins know who you are from one logon to the next,

when your IP address is different each time?

At least that was my interpretation.

Lol, yes this is my question.

Here is a utility that I use

http://www.sysinternals.com/Utilities/PsLoggedOn.html

I use http://www.callingid.com/ 's toolbar to find out who owns the sites i view and where they're from, but I guess you're looking for something in the opposite direction, how the site knows who you are and where your from... lol!