.roll_top,.fall{position:relative;cursor:pointer;height:11px;width:18px;z-index:106;overflow:hidden}
.roll_top{background:url(../images/gotop.gif) no-repeat}
.roll_top.hoverClass{background:url(../images/gotop.gif) no-repeat 0 -22px}
.fall{background:url(../images/gotop.gif) no-repeat 0 -10px}
.fall.hoverClass{background:url(../images/gotop.gif) no-repeat 0 -32px}
#roll{display:none;width:18px;position:fixed;top:300px;_position:absolute;_margin-top:300px;_top:expression(eval(document.documentElement.scrollTop))}