.top{width:100%; border-bottom:1px solid #ccc;}
.top .nav
	{
    width:500px;
    height:150px;
  	margin:0  auto;
    position:relative;
		top:75px;    background:url(http://p0.so.qhmsg.com/t017112541dbb88f025.jpg) no-repeat 0 -374px;}