<div class="backToTop" title="返回顶部">返回顶部</div>

.backToTop {    display: none;    width: 18px;    line-height: 1.2;

    padding: 5px ;

    background-color: #;

    color: #fff;

    font-size: 12px;

    text-align: center;

    position: fixed;

    _position: absolute;

    right: 10px;

    bottom: 100px;

    _bottom: "auto";

    cursor: pointer;

    opacity: .;

    filter: Alpha(opacity=);

}

(function() {

    var $backToTopTxt = "返回顶部", $backToTopEle = $('<div class="backToTop"></div>').appendTo($("body"))

        .text($backToTopTxt).attr("title", $backToTopTxt).click(function() {

            $("html, body").animate({ scrollTop:  }, );

    }), $backToTopFun = function() {

        var st = $(document).scrollTop(), winh = $(window).height();

        (st > )? $backToTopEle.show(): $backToTopEle.hide();

        //IE6下的定位

        if (!window.XMLHttpRequest) {

            $backToTopEle.css("top", st + winh - );

        }

    };

    $(window).bind("scroll", $backToTopFun);

    $(function() { $backToTopFun(); });

})();