<!DOCTYPE html>
<meta charset="utf-8">
<title>tab选项卡学习</title>
<style>
html,body,ul,li{padding:0;margin:0}
ul{list-style-type:none}
clear{ clear:both;}
.box{ 960px; height:2000px; margin:0 auto; background:#999;}
span{ position:fixed; _position:absolute; top:0; left:0; 20px; border:1px solid #666; display:none;}
</style>
<div class="box"></div>
<span>返回顶部</span>
<script src="jquery-1.8.3.min.js"></script>
<script>
$(window).scroll(function(){
var ws=$(window).scrollTop(),
wh=$(window).height(),
nw=$(window).width(),
lv=(nw-960)/2+970,
xx=$('span').height()+120;
//console.log(ws);
if(ws){
$('span').show().css({left:lv,top:wh-xx});
if($.browser.msie&&($.browser.version === "6.0")){
$('span').css("top",wh-xx+ws);
}
}else{
$('span').hide();
}
});
$('span').click(function(){
$(window).scrollTop(0);
});
</script>