OS X :: Small Black Line On Corner Of Screen

So today I noticed a small black bar on the corner of my screen. I tried to get a screen shot of it, but i couldn't, like it was off the screen. However, my mouse dissapears under it when i move it there.It is a little hard to distinguish because it is the 2.4 ghz macbook aluminum, glossy screen so it has the black surrounding it, but it is definably there. This all along the right hand edge of the screen.

Although there is a chance it may have always been there, I am not so sure. I think there are lines along the top and left hand sides, but they are much smaller. again it is hard to tell. I am fairly sure that there is none on the bottom of screen. Is this normal, or what? I have applecare, and I didn't do anything to my macbook. Although it is getting me a little OCDish, and is slightly annoying, and I know these things on the screen tend to expand.