方法1：
<html>
<head>
<title></title>
<script language="javascript" type="text/javascript">
window.onload = function() {
var div = document.getElementById("csdn");
div.style.position = "absolute";
div.style.top = "0";
div.style.height = document.documentElement.clientHeight;
}
</script>
</head>
<body>
<div id="csdn" style="background-color: #FF0000; width: 200px;">
1234567890-=<br />
1234567890-=<br />
</div>
</body>
</html>
2. 方法2
方法1在有些场合还是无法解决问题，
var height = document.documentElement.scrollHeight; if (height > 30) { height = height - 30; $("body").css('height', height); } }
这里使用了 document.documentElement.scrollHeight
