易迅飞顶部的css，js，html

<div id="j_backtop" class="mod_backtop"><a ytag="72300" title="回顶部" href="javascript:">回顶部</a></div>

/*-----------------------------返回顶部css开始-----------------------------*/
.mod_backtop{position:fixed;z-index:997;right:20px;bottom:50px}
.mod_backtop a{overflow:hidden;display:block;width:50px;height:50px;background:url("http://static.gtimg.com/icson/img/common/backtop.png") no-repeat 0 0;text-indent:-999px;opacity:.7;filter:alpha(opacity=70)}
.mod_backtop a:hover{background-position:0 -52px;opacity:1;filter:alpha(opacity=100)}
/*-----------------------------返回顶部css结束-----------------------------*/

//------------------------飞顶部js开始-----------------------------
$(function(){
var a = $("#j_backtop");
if (0 < a.length) {
var b = document.documentElement.clientHeight || document.body.clientHeight,
c = Math.min(b, 500);
$(window).bind("scroll resize",
function() {
var d = $(this).scrollTop();
d < c ? a.fadeOut() : a.fadeIn();
$.browser.msie && ("6.0" == $.browser.version && !$.support.style) && a.css({
top: b - 200 + d
})
});
a.click(function() {
$(window).scrollTop(0);
return ! 1
})
}
})
//------------------------飞顶部js结束-----------------------------