Navigation links alignment problem in IE 6/7 but in IE 8 it works.

In IE 8 my navigation links are centered in in the navigation image. In IE 6/7 They just simply wouldn't center like it does in IE 8.
 
Here is the CSS Code for IE 6
<code>
 
/*Header*/
#header h1 {
	padding-bottom: 0; 
	line-height: 13px;
}
 
 
/*Nav*/
#nav {
	width: 637px;
	margin-left: 305px;
	height: 100%;
 
}

/*Header*/
#header h1 {
	height: 92px;
	width: 304px;
	margin-right: 300px;
	margin-bottom: -89px;
	line-height: 18px; 
}
 
img {
	border-style: none;
}
/*Nav*/
#nav {
	width: 637px;
	height: 91px;
	margin-left: 305px;
	margin-bottom: 25px;	
}