#back-to-top{
	position:fixed;
	right: 20px;
	bottom: 20px;
	display: none;
	z-index: 999999;
}
	#back-to-top a{
		width: 50px;
		height: 50px;
		display: block;
		overflow: hidden;
		text-indent: -999px;
		background: url(http://www.lightingchina.com/images/back-to-top.gif) 0 0 no-repeat #9f9f9f;
	}
	#back-to-top a:hover{
		background-position: -50px 0;
		background-color: #666;
	}