Code to display different versions of website to different users

We have a website. Lets say this website has 5 different pages, each that contain several pieces of information, like the price of our service. We have two different versions of each of these 5 pages, (Version A of the site has the price at $50, and Version B has the price at $75). I want the website to give version A to half of the visitors and version B to the other half. I need some code that will do this. Note: It is important that a user not be able to simply refresh and see the different versions, EVEN IF THEY HAVE COOKIES TURNED OFF. Step 1- Decide on an algorithm to make the random decision. The seed for the Random Number Generator could be: IP Address, ISP, MAC Address, etc. Step 2- Write code that uses this algorithm to display our page. Our website is currently being developed and will be based off of the Joomla! CMS. I will have the web designer take care of creating the different versions of the pages....all I want is code that will select between them. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows? (depending on the nature? of the deliverables): a)? For web sites or? other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software? installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform all web browsers.