A request for a page is received. A processor is used to provide an optimized version of the page at least in part by determining dynamically an optimized content element for the page based at least in part on a user attribute associated with the request and content performance data generated based at least in part on testing of alternative versions of the page with respect to other users having the user attribute. The provided optimized version of the page is selected from the alternative versions of the page based on the content performance data indicating that the selected version of the page is optimized for the other users having the user attribute.