User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0 Build ID: 20150319201009 Steps to reproduce: Switch between tabs. In the attached image, I switched from Wikipedia to Gmail. This bug occurs randomly, but frequently enough that I experience it several times per day, and on both computers I use regularly: -Windows 7 64 bit -Windows 8 64 bit Actual results: Some of the contents of the previous tab continue to be rendered after switching tabs. Interacting with individual elements in the current tab causes them to be rendered properly. For instance, a textbox might at first be covered up with stuff from the previous tab, but when mousing over it or clicking on it, it begins to be rendered properly. Resizing the window causes everything to be rendered as expected. Expected results: After switching to a new tab, only the new tab should be rendered.