backToTop.js：

(function () {    var $backToTopEle = $('
     
').appendTo($("body"))        .click(function () {            $("html, body").animate({ scrollTop: 0 }, 120);        }), $backToTopFun = function () {            var st = $(document).scrollTop(), winh = $(window).height();            (st > 0) ? $backToTopEle.show() : $backToTopEle.hide();            //IE6下的定位            if (!window.XMLHttpRequest) {                $backToTopEle.css("top", st + winh - 166);            }        };    $(window).bind("scroll", $backToTopFun);    $(function () { $backToTopFun(); });})();

样式设置：

.backToTop {
       display: none;    background:url(../images/go_top.gif);    background-repeat:no-repeat;    background-position:0px 0px;    width:50px;    height:50px;    color: #fff;    font-size: 12px;    text-align: center;    position: fixed;    _position: absolute;    right: 2px;    bottom: 2px;    _bottom: "auto";    cursor: pointer;    opacity: .6;    filter: Alpha(opacity=60);}.backToTop:hover{
       background:url(../images/go_top.gif);    background-repeat:no-repeat;    background-position:0px -100px;}