black horizontal line on screen
No shock on computer whatsoever, it appeared suddenly. It's crossing my screen on the lower quarter of the 13" screen. Have tried to press the screen as read on posts, it does not affect the line not its appearance. It does not appear when I connect the computer on another monitor (but still is on the computer's screen). Have checked software update, reboot, safe mode, PRAM reset, etc.
What can I do before bringing it to the Apple Store?