I've made this little program, called IPrefer. There is a problem most web programmers have encountered. It is alarming how it spread like cancer over the net. Browers increasingly remove or alter the environment settings, making it a security hole that shouldn't go unnoticed. Some servers also have problems with this, and leave it blank, no matter how you try to get this to show anything but a blank line... It's not always the HTTP_REFERER works, in fact it hardly works at all... So I wrote this little function to get a sense of security back.
Download it on http://www.starhiker.net/iprefer.zip. Note: This is first version, don't expect it to be perfect... Check it out, and tell me what you think.