css:

.wraper{
    width:980px; height:2048px; margin:0 auto; background:#ccc; }/*返回头部*/#backToTop a{
    display:block; cursor:pointer;width:25px; height:26px; text-indent:-9999em; position:absolute; left:0; top:0; z-index:10;}#backToTop .bt_bg{
           background:url(http://i0.cy.com/xtl/main/20140227/backTop.png) no-repeat;_background: 0; _filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='http://i0.cy.com/xtl/main/20140227/backTop.png',sizingMethod='scale');         width:25px; height:26px ; position:absolute; left:0; top:0; z-index:8; }#backToTop {
    display:none; width:25px; height:26px ; position:fixed; right:50%; margin-right:-533px; bottom:110px; z-index:1; }/**针对ie6设置*/*html #backToTop {
    position:absolute; margin-top:expression(0 - parseInt(this.offsetHeight / 2) + (TBWindowMargin = document.documentElement && document.documentElement.scrollTop || document.body.scrollTop) + 'px');}

 

html:

 

javascript：

$('body').append($('
     
      回到顶部
      
     
').hide(0));    $(window).scroll(function(){        $('#backToTop').show();        if ($(document).scrollTop() != 0)             $('#backToTop').show();        else             $('#backToTop').hide();    });    $('#backToTop a').click(function(){        $('html, body').animate({            scrollTop: 0        }, 800);        return false;    });