<p id="back-to-top"><a href="#top"><span></span>返回顶部</a></p>

/*returnTop*/

p#back-to-top{

    position:fixed;

    display:none;

    bottom:100px;

    right:80px;

}

p#back-to-top a{

    text-align:center;

    text-decoration:none;

    color:#d1d1d1;

    display:block;

    width:64px;

    /*使用CSS3中的transition属性给跳转链接中的文字添加渐变效果*/

    -moz-transition:color 1s;

    -webkit-transition:color 1s;

    -o-transition:color 1s;

}

p#back-to-top a:hover{

    color:#979797;

}

p#back-to-top a span{

    background:transparent url(/static/imgs/sprite.png?1202) no-repeat -25px -290px;

    border-radius:6px;

    display:block;

    height:64px;

    width:56px;

    margin-bottom:5px;

    /*使用CSS3中的transition属性给<span>标签背景颜色添加渐变效果*/

    -moz-transition:background 1s;

    -webkit-transition:background 1s;

    -o-transition:background 1s;

}

#back-to-top a:hover span{

    background:transparent url(/static/imgs/sprite.png?1202) no-repeat -25px -290px;

}

<script src="http://ajax.microsoft.com/ajax/jQuery/jquery-1.7.2.min.js"></script>

<script>

$(function(){

        //当滚动条的位置处于距顶部100像素以下时，跳转链接出现，否则消失

        $(function () {

            $(window).scroll(function(){

                if ($(window).scrollTop()>100){

                    $("#back-to-top").fadeIn(1500);

                }

                else

                {

                    $("#back-to-top").fadeOut(1500);

                }

            });

            //当点击跳转链接后，回到页面顶部位置

            $("#back-to-top").click(function(){

                $('body,html').animate({scrollTop:0},1000);

                return false;

            });

        });

    });

</script>