The HTTP_REFERRER code works great in letting me know where users are coming from but the above line pops up every once in a while. I would like to know how some users can mask the referring url.
or if you use a local proxy to intercept the outbound browser traffic, you can set this to whatever you like! @stake used to have a free one 'WebProxy' - you may be able to find versions of it around, or pay for the new one (or simply write your own - rocket science it is not)