User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 Build ID: 20150122214805 Steps to reproduce: Opened a website displaying a video that can be displayed in fullscreen (youtube, dailymotion, vimeo, etc). Launched the video, made it fullscreen by using control on the video. Then leaving the fullscreen mode using escape. Actual results: My bookmarks box that was opened on the left side disappeared, I had to make it reappear. Expected results: The bookmarks box on the left side shouldn't have disappeared.