Thick Horizontal Line on Screen

Hi, I'm new to this forum and to the Mac. I have a new white macbook 13" (the late October 2009) version and since I got it the screen shows a thick line (around 1-2 centimeters) from time to time when I open up a new page. It is not permanent and disappears when I scroll the screen up and down or refresh the page. The color of the lines are from the background of the pages I open. So, if the background page is orange, there would be a thick orange line appearing somewhere on the screen when I open the page and it would disappear when I scroll down the page. Again, this does not happen every time. Mostly once in a while.

There is nothing major but I just would like to make sure if this is common for a Mac or I should have someone look at it.

Thank you very much. I really appreciate all your inputs .

This is not a common problem and if it is not due to Physical Damage make a Genius appt and get that fixed, Before the 1 year expires of warranty. I migh add it is pretty easy to replace that screen, but if u can have apple fix it that is all around better, because that is the easiest route for u. it seems to be a delay in the those pixels, is it similiar to a burn in on a Plasma Screen TV? none the less get apple to fix it.