Layer background problem with mozilla 1.6

[Ogg]

Hi. I'm trying to use a background image for a layer. and I want it to repeat only verticaly. Here is my code:

#c1 {
	position: absolute;
	padding: 0px;
	width: 690px;
	height: 100%;
	left: 50%;
	margin-left: -345px;
	background: #fff url(resimler/bg.jpg)   top left repeat-y;
}

Works good with IE and Opera, but with Mozilla, there are a big gap at the bottom of the page (i think it's height is same with height of background image. Is there a way to solve this problem, or am I doing something wrong?

Thanks. And sorry for my terrible English.