网页显示布局问题。求助！

先上代码
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>文档阅览</title>    
</head>
<body >
    <form id="form1" runat="server" style="height:100%; width:100%">
        <div style="width:100%; height:100%">
        <object classid="clsid:CA8A9780-280D-11CF-A24D-444553540000" id="PDF1" name="PDF1" style="width:100%; height:100%" border="0">     
            <param name="SRC" value="<%=FilePath %>"/>
        </object>
        </div>
        <script language="JavaScript" type="text/javascript">                       alert(document.body.clientHeight); //此处获取的高度是192            document.getElementById("PDF1").height = document.body.clientHeight;
            document.getElementById("PDF1").width = document.body.clientWidth;
        </script>
    
    </form>
</body>
</html>红色处为什么是192呢（IE8下面）？在IE6下面显示就正常！！求助！