Sorry about not having the option to post images with your question. You can post some by replying to yourself until that feature is added. Do you notice these lines when scrolling? Does it occur primarily when the page contains videos? Try turning off these features: * Smoothing scrolling * Autoscrolling * Firefox hardware graphics acceleration orange Firefox button ''or'' classic Tools menu > Options > Advanced > "General" mini-tab Then restart Firefox. Any improvement? If it is only video related, consider this option: * Disable Flash hardware graphics acceleration You can toggle the hardware acceleration setting using the steps in this article: http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues Any luck?

See also: *https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers