(function () {

    var $backToTopEle = $('<div class="backToTop"></div>').appendTo($("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(); });

})();

.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;

}