[Zope] Where does <the client> come from...?

I would like to learn if it is possible to tell where the client comes from...? And if so: how...? I know the HTTP_USER_AGENT global variable but is there something like that which tells you the URL the client is comming from...? I also know about javascript:history.go(-1), but can somebody tell me how I read the URL from the back-page something like: javascript:history.href(-1)...? ( = Stoons = ) - Webmaster @ 3D festival (http://www.3dfestival.com)