Galen
With Galen Framework, layout testing can be automated to save you a lot of manual work. With its own specification language (Galen Spec), you can write tests to verify the correct look of the web page as well as the location and alignment of specific elements on a page.
So, you can write simple tests such as "The button should be green" as well as more complex behavior specifications such as "On mobile devices the button should be inside the viewport". Especially when testing a responsive website on multiple devices, browsers and resolutions, the manual testing effort gets expensive. To help with that, Galen runs its specifications fully automated with Selenium against the required browsers and devices.
Whenever a test fails Galen writes a test report with screenshots to show the mismatching areas on the page to help testers and developers become aware of the problem.
At AOE, the Galen Framework helps us to continuously test the UI for potential regression bugs introduced by new features.