让Iframe自适应高度

<iframe src="b.html" marginheight="0" marginwidth="0" frameborder="0" scrolling="no" width="100%" height="100%" id="iframepage" name="iframepage" onload="SetWinHeight(this)"></iframe>

<script type="text/javascript" language="javascript">
//<![CDATA[
function SetWinHeight(obj)
{
var win=obj;
if (document.getElementById)
{
if (win && !window.opera)
{
if (win.contentDocument && win.contentDocument.body.offsetHeight)
win.height = win.contentDocument.body.offsetHeight;
else if(win.Document && win.Document.body.scrollHeight)
win.height = win.Document.body.scrollHeight;
}
}
}

//]]>
</script>