According to Google “Website Optimizer, Google’s free multivariate testing application, helps online marketers increase visitor conversion rates and overall visitor satisfaction by continually testing different combinations of site content (text and images).”
So, after I looked up what the word multivariate meant I then checked out the demo.
This free new tool comes with a Google AdWords account and lets you rotate and track ROI on webpage variations. The example they present is scenario with three different homepages that only differ by a unique headline, photo and paragraph of copy. These pages are then auto rotated and tracked by Google whose analytics reveal which message is the most effective. Try it out.
Google Website Optimizer