Workaround for Fullscreen Issues
My new fullscreen update allows you to test sites as they would look if you loaded them normally. Unfortunately, as these pages are not affiliated with the Tester, some may not properly support this feature. Luckily, there is a workaround for this issue. In this guide, you will learn how to access full screen mode, and a trick to use when this doesn't work as intended.
How to Activate/Escape Full Screen Mode
Activating full screen mode for any of the sites is very simple! All you have to do is press the “Toggle Full Screen” button above or to the right of the embedded sites. To exit this view, simply press the esc key.
Workaround: Full Screen Issues
Due to the nature of certain sites, full screen mode may simply move the embedded site to the corner and fill the rest of the screen with black. Luckily, there is an easy workaround for this. Simply hold down the ctrl key (cmd if you're on Mac) and keep hitting the + until the site is adequately sized. I recommend 125% zoom. If you want to zoom out again, hold down ctrl and hit the - key.