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

p#back-to-top{  position:fixed;  bottom:100px;  right:80px;}p#back-to-top a{  text-align:center;  text-decoration:none;  color:#d1d1d1;  display:block;  width:30px;  /*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:color1s;  -webkit-transition:color1s;  -o-transition:color1s;}p#back-to-top a:hover{  color:#979797;}p#back-to-top a span{  background:#d1d1d1 url(../images/arrow_up.png) no-repeat center center;  border-radius:6px;  display:block;  height:30px;  width:30px;  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:background1s;  -webkit-transition:background1s;  -o-transition:background1s;}#back-to-top a:hover span{  background:#979797 url(../images/arrow_up.png) no-repeat center center;}

<script type="text/javascript">$(document).ready(function(){ //首先将#back-to-top隐藏 $("#back-to-top").hide(); //当滚动条的位置处于距顶部600像素以下时，跳转链接出现，否则消失 $(function () {  $(window).scroll(function(){   if ($(window).scrollTop()>600){    $("#back-to-top").fadeIn(500);   }else{    $("#back-to-top").fadeOut(500);   } }); //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},500);   return false;  }); });});</script>