$(document).ready(function() {
    var $backToTopTxt = " ", $backToTopEle = $('<div class="backToTop"></div>').appendTo($("body"))
    .text($backToTopTxt).attr("title", $backToTopTxt).click(function() {
    $("html, body").animate({ scrollTop: 0 }, 120);
    }), $backToTopFun = function() {
    var st = $(document).scrollTop(), winh = $(window).height();
    (st > 0)? $backToTopEle.show(): $backToTopEle.hide();
    //IE6ϵĶ¨Î»
    if (!window.XMLHttpRequest) {
    $backToTopEle.css("top", st + winh - 166);
    }
    };
    $(window).bind("scroll", $backToTopFun);
    $(function() { $backToTopFun(); });
})