<iframe>标签自适应高度和宽度

<script type="text/javascript" language="javascript">   
function iFrameHeight() {   
var ifm= document.getElementById("iframepage");   
var subWeb = document.frames ? document.frames["iframepage"].document : ifm.contentDocument;   
if(ifm != null && subWeb != null) {
   ifm.height = subWeb.body.scrollHeight;
   ifm.width = subWeb.body.scrollWidth;
}   
}   
</script>