how detect the url of my visitors?

FOTO FILM (fotofi25@teleline.es)
Sat, 14 Aug 1999 08:48:50 +0200

Date: Sat, 14 Aug 1999 08:48:50 +0200
From: FOTO FILM <fotofi25@teleline.es>
To: java-security@java.sun.com
Subject: how detect the url of my visitors?

Hello,

I'm a beginer developer of java software and i would detect de url and
email (if is possible) of the visitors of my web page with applets java.

I do it?
How?

Thanks, Jaume
fotofi25@teleline.es