Why do I have a line on my stomach!?

Ok, so I have relatively ok abs, I mean nothing big, but no fat, but I have this line on my stomach, because I have a slight slouch, so my skin folds and there is this ugly crease! Here's a picture! a href="http://www.webcampicture.com/image.php?id=0525wb50ra8s" rel="nofollow"http://www.webcampicture.com/image.php?i…/a Ok is says my location....just ignore that... Like new Scooby Doo pajamas? Haha, anyways, whats with the line!!!! How do I get rid of it!!!