I can almost guarantee it's simply a split test using a cookie, as that's the standard way to experiment (using Google Website Optimizer and others). It's a co

I can almost guarantee it's simply a split test using a cookie, as that's the standard way to experiment (using Google Website Optimizer and others). It's a common bracketing experiment. Edit: To be clear, if it's flash cookies it could persist after browser installs but still be different per browser.