OS X :: 24" IMac Faint Vertical Line Of Pixels On The Screen?

i noticed a faint vertical line of pixels on the far left of my screen. they weren't black or colored, just faint/dim. i tried switching my desktop background, and the line was still there. i restarted my computer, and the line was still there. i shut down the computer, thinking that i would find the line there in the morning and have to take it to the apple store.

when i turned the computer on the next morning, there was no line. however, later that evening i noticed a reappearance of the line. i restarted the computer and left for a while. when i came back later, i woke the computer from sleep mode, and the line was gone.

there was no line on the computer this morning, although after a couple hours of use, i noticed that two lines had developed on the edge of where i had application windows open -- in this case, both yahoo messenger for mac. curiously, this didn't happen with other windows (finder, safari, etc).