I've been using $_SERVER['HTTP_REFERER'] with PHP for some scripts on my site. It works about 50%-60% of the time.
Someone told me that the "server sees more" about where someone is coming from than $_SERVER['HTTP_REFERER'] can ... then the jerk disappeared without elaborating!
Does anyone know what he's talking about? Is there something I can do with the server to channel facebook traffic to a certain page on my site that will have a higher success rate of recognising traffic from facebook?