#scrolltop{visibility:hidden;position:fixed;bottom:100px;display:block;margin:-30px 0 0;width:56px;height:56px;background:url(../images/top_ding.png) no-repeat 50% 0;line-height:999px;opacity:.40;filter:alpha(opacity=40);overflow:hidden;cursor:pointer;}
.ie6 #scrolltop{position:absolute;bottom:auto;}
#ft{margin:0 auto;width:996px;}