Basically, the tool lets web publishers try out different designs on their web page to see which one performs best. Want to see which ad unit is more likely to get people to click? Want to see which RSS icon is more likely to get people to subscribe to your site's feed? Google Website Optimizer will let you set up an experiment and track the results.
There's also a new Google Website Optimizer blog that you can follow for news and tips related to the tool.
[via Google Blogoscoped]
