If I enter www.medicare.gov in the navigation bar or select it on a Google search the website displays in a manner similar to full screen mode. However, if I remove the www and enter medicare.gov the website displays normally. I have tried these combinations on various websites but haven't recreated the problem. I was scrolling on the website when it suddenly expanded to the similar to full screen display although the tool bars remain intact. I have cleared caches, restarted Firefox in safe mode, cleared history, etc., to no avail. I am running Firefox Beta 24.0.1