I found a link that I'm trying to understand. It started out cloaked using a URL shortener, but my browser displays the URL as it passes. Then the URL changes totally and I end up at a totally different web site. After the URL is past the URL shortener The format looks like this. http://domain.net/Page-URL/?mn=1234 Way I figure it they're hopping the surfer to the new site using the ?mn=(x). If I edit it out then I get the page at http://domain.net/Page-URL/. Understanding the ?mn= is just the first part of the question. The second part involves selective usage of the forwarding. Can it be filtered to allow a particular IP to end up on the http://domain.net/Page-URL/ page and forward everyone else to the alternate page?
It all depends on the coding behind it. the url shortener site will either use frames (with advertising) or will use something like PHP's "header" command to redirect the page the ?mn= is additional info, usually just an affiliate id so that right person gets paid if you purchase. In the old days it might have been a page name but for the scenario you describe it'll be an affiliate. Because the forwarding is being done on the server (ie header) and not on the page (ie meta refresh) all sorts of factors can come into play. Lets say my sales program didn't want to include parts of Asia - those users would be redirected to a seemingly official but pointless page and they would have no offer to join. Those from approved countries would see the sales page with a registration or purchase form. The problem with approach is that other countries can get caught in the net. Block all APNIC countries and you lose a lot of Asia but you also lose the normally allowed Australia and New Zealand. You might also only want to allow X number of signups per affiliate per day/week/ever and so you'd look at their count as they come through and decide on the page you will show depending on the answer. Once you get into a bit of PHP programming go and have a look at the $_SERVER variable and the information it holds. There are lots of cool (but normally unnecessary) things you can do.