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

[3dfestival - WebMaster]

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)