<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
body{margin:0; padding:0}
#to_top{
width:30px;
height:40px;
padding:20px;
font:14px/20px arial;
text - align: center;
background: #06c;
position: absolute;
cursor: pointer;
color: #fff;
}
</style>
</head>
<body style="height:1000px;">
<h1>返回顶部</h1 >
<div id = "to_top"> 返回顶部
</div>
</body>
</html>
<script type="text/javascript">
window.onload = function(){
var oTop = document.getElementById("to_top");
var screenw = document.documentElement.clientWidth || document.body.clientWidth;
var screenh = document.documentElement.clientHeight || document.body.clientHeight;
oTop.style.left = screenw - oTop.offsetWidth +"px";
oTop.style.top = screenh - oTop.offsetHeight + "px";
window.onscroll = function(){
var scrolltop = document.documentElement.scrollTop || document.body.scrollTop;
oTop.style.top = screenh - oTop.offsetHeight + scrolltop +"px";
}
oTop.onclick = function(){
document.documentElement.scrollTop = document.body.scrollTop =0;
}
}
/**jquery的写法实现返回顶部
jQuery("#to_top").click(function(){
jQuery("html,body").animate({'scrollTop':0},100)
})
**/
</script>
