为什么window.innerHeight和document.body.clientHeight的值会不一样呢？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<script type="text/javascript">
document.write(window.innerHeight+"<br/>"+window.innerWidth+"<br/>");
document.write(document.body.clientHeight+"<br/>"+document.body.clientWidth);
</script>
</body>
</html>
