Our Responsive Design Checker is built to do one thing very well: show you how visual elements of your site respond to different screen sizes.
It won’t show you how various technologies function within your site, so you can’t use it to test things like Flash or video players. Sites that don’t play well with iFrames, including Google, Pandora, and Facebook, will either appear as white boxes or navigate you away from the Responsive Design Checker, and you don’t want that!
This tool isn’t intended to test mobile site versions, so it won’t show you if your site redirects to a mobile version. Some devices, including the iPhone, automatically resize websites to fit the screen, but thats not responsive design, so you won’t see that here, either.