Proven in a test
It checks its own pages in a real browser
A page can be opened in a real browser on a phone-sized and a desktop-sized screen and checked for problems such as a broken image, text running off the screen or a hidden button. On 14 October we broke an image on purpose. The check caught it on both screens, an agent replaced it, and a second check came back clean. The whole loop took 27 minutes and cost $0.06.
It has not yet run on a page that was not set up as a test. When it does, the result will be shown here.
