Hi, Hope someone can advise. Pics at bottom. Today i noticed when i was watching a youtube video in full screen there was a horizontal bar going across top of my screen all the way across except there was about an inch each side where the horizontal line was not showing. Thinking it was youtube or the video itself i tried a video on vimeo and the same as above. I then decided to change my desktop background to 'solid black' and choose to use 'Dark menu and Dock' from 'General' as not noticeable on light backgrounds, whilst at it i decided to check the option 'Automatically hide and show the menu bar' as it makes it easier to see. As you can see in the images there's a a very faint horizontal bar going across the top of my screen minus about an inch each side where it does not show. I tried Apple diagnostics, reset NVRAM and SMC problem still there. I logged out of my standard account which i use all the time on a daily basis and logged into my administrator account thinking maybe it maybe something to do with my account and problem still there. I got into a chat with an Apple rep online and he said he could see what i meant and booked me an appointment for a week today (Saturday) at my local Genius Bar. He said did i try safe mode and i said no as to be honest i didn't think of Safe Mode, anyhow i booted into safe mode and the problem is gone regardless of whether i'm logged in to my standard account or administrator account. I'm not sure what the problem could be. I noticed it a few weeks ago but thought it was a video on youtube until i watched another youtube video and then investigated further as above. No kernel panics or anything else from what i can tell except since doing a fresh clean install of El Capitan, when i choose to restart computer screen goes black and take allot longer until i hear the chime. Seems to take longer to restart basically but assume this is likely El Capitan and not a hardware issue as did not have long restarts in Yosemite. Does anyone have the same problem, could you please check? is it a glitch in OS X, GPU driver glitch perhaps or hardware problem ie. GPU/Screen? I've kept my appointment still incase it's a hardware problem and will get it checked but baffled to be honest. Thanks for any advice etc.