#roll_top, #fall, #ct
{
	position: relative;
	cursor: pointer;
	height: 52px;
	width: 52px;
}
#roll_top
{
	background: url(../images/top.png) no-repeat;
}
#fall
{
	background: url(../images/top.png) no-repeat 0 -80px;
}
#ct
{
	background: url(../images/top.png) no-repeat 0 -40px;
}
#roll
{
	display: block; position:fixed; right:20px; bottom:50px;
	width: 52px;
 
	_bottom: expression(eval(document.documentElement.scrollTop));
}