In any given month, we experiment with hundreds of subtle variations of the Google search results page, testing everything from font sizes and colors to layouts and spacing, as well as dozens of other variables. Recently, we found that by standardizing the look of the URLs on the page, we were able to improve many of our user metrics, including ad clickthrough rates.

As a result, we've decided to update the appearance of the display URLs of all ads that appear on search results pages in the next week or so. Following the change, the domain portion of your display URL will always be shown in lowercase letters. For example, if your display URL is Subdomain.Example.com/Subdirectory, it will appear as subdomain.example.com/Subdirectory.

There’s no need for you to make any edits to your ads. All uppercase letters in your display URL domain will automatically be changed to lowercase when your ad is served.

As you've probably figured out by now, we believe that regular website testing is the best way to ensure an optimal user experience, and we encourage you to test variations of your own website. Learn how you can start testing with our Website Optimizer tool.

Posted by Lisa Shieh, Inside AdWords crew