Yesterday I suddenly discovered a vertical line on my Macbook Air screen towards the left side of the display. The red, one pixel line simply showed up when I opened the laptop while traveling in the morning…
I tried a couple fixes, some people even suggested the problem is caused by hardware failure. Fortunately the solution was quite simple, resetting the PRAM. Simply restart your computer while holding Command+Option+R+P simultaneously BEFORE the grey screen appears and UNTIL you hear an additional chime, release and voila, no more line.