<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>无标题文档</title>
<style>
/*默认样式，主要是position:fixed实现屏幕绝对定位*/
#gotoTop{position:fixed;top:75%;left:50%;cursor:pointer;margin-top:-50px;margin-left:520px;padding:9px 4px;width:20px;text-align:center;border:1px solid #e0e0e0;background:#fff;display: none;}
/*用CSS表达式(expression)来实现ie6下position:fixed效果*/
#gotoTop{_position:absolute;_top:expression(documentElement.scrollTop + documentElement.clientHeight * 3/4 + "px")}
/*鼠标进入的反馈效果*/
#gotoTop.hover{background:#5CB542;color:#fff;text-decoration:none;}
</style>
</head>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p><p>1</p>
<div ></div>
<script src="http://ajax.microsoft.com/ajax/jQuery/jquery-1.7.2.min.js"></script>
<script>
function gotoTop(min_height){
//预定义返回顶部的html代码，它的css样式默认为不显示
var gotoTop_html = '<div ).fadeOut(100);
};
});
};
gotoTop();
</script>
</body>
</html>