System > Configuration > Sales > Google API - Google Website Optimizer
Google Website Optimizer is a free tool that is used to test the effectiveness of one page against another. Such “A/B”tests can be used to test designs, concepts, the positioning and wording of promotions, and the presentation of products in your store. The Google Website Optimizer configuration setting is used to enable or disable Google Website Optimizer for your product and category pages. When enabled, the “Product View Optimization” tab appears on all product and category pages so you can enter Google Website Optimizer scripts.
For step-by-step instructions, see: “Setting Up Google Website Optimizer”
Before you continue, make sure to set the correct configuration scope for your store, if necessary. For more information, see: Understanding Store Scope.