The Inside AdSense Team released a special JavaScript code today that you can use to do A/B testing without requiring server-side scripting. This means that anyone can use this code and do testing, no matter what your server configuration. Previously, to ensure that the ad code isn’t modified, publishers were forced to use a scripting language like PHP, ASP, or ColdFusion to achieve this effect. They’ve approved the JavaScript template below, which reotates between the two ad units, showing each 50% of the time. You’re free to modify the AdSense code for use with this specific script for the purposes of A/B testing, according to their policy folks. If you want to test different ad formats, but have the client-side handle it, this is your solution.