OK so I'm using my fresh out the box MBA 13 on it's third day, and today for the first time I've noticed this white line, very distinct, which appears across the screen. The 2 times it has happened i've been using Safari full screen and swiped out of it to a finder folder which was open and I saw it across the icons, the second time I've gestured into Mission Control and it was very very visible across the background, looked horrible and scary 
Is this a hardware fault, or more of a software glitch? I haven't updated to Mavericks, and my 13" screen is a Samsung Panel, which was on medium brightness.
Is this a hardware fault, or more of a software glitch? I haven't updated to Mavericks, and my 13" screen is a Samsung Panel, which was on medium brightness.