It uses cookies to store participation and conversion data, so as a visitor you'll come away with a cookie that looks like this: ab:ID=1212802769|Tests=heade

It uses cookies to store participation and conversion data, so as a visitor you'll come away with a cookie that looks like this: ab:ID=1212802769|Tests=header_caption,register_payment_message,account_instructions,setup_navigation|Conversions=header_caption That way, we can simply ask the visitor whether he's participating in a given test, and we can know not to score him twice for anything. All that lives on the server is a file at the root called tests.ab holding a few k worth of participation and conversion tallies. Every time anything changes, it checks to see if it's saved its state in the last minute, and if not it simply serializes itself to XML and dumps that to disk. If it ever finds itself uninitialized (such as on a server reset), it attempts to load its last saved state. So long as you remember to ignore that tests.ab file as part of your deploy, it'll survive intact. As to selling it, I'm all about bringing in the cash, but a hosted option wouldn't really work for this. First, it's architected specifically so there's hardly anything to host. Second, its big advantage over something like Visual Website Optimizer is that your pages don't hang while requesting resources from a 3rd party. Don't worry. I've got other stuff bringing in revenue (like the site this is hosted on, for instance), but thanks for the suggestion!