MacBook Air :: Horizontal Marks On Screen From Keyboard Recess

Just what I needed - another thing to obsess about! On my screen, corresponding to where the bottom line of the keyboard recess is, I have a horizontal marks on my screen. Does anyone else have this? I've tried buffing with some iKlear and a soft cloth but it won't go away. I can't see it when the screen's on but it's bugging me now, as these things tend to do. With my old Powerbook I kept the plastic sheet in between the sceen and keyboard but assumed this was not necessary with the recessed keyboards. Now it seems its the edge of the recess, rather than the keys themselves, which is the problem.