<script type="text/javascript">
//<![CDATA[
window.onload = function() {
var f = document.getElementById("mainframe");//Sets iframe id
function resize() { //Starts resize function
var h = "";
var w = "";
if (f.contentDocument) {
h = f.contentDocument.documentElement.offsetHeight + 20 + "px";
// can't find anything for Opera and Firefox that works for the width. OffetWidth doesn't work right either.(f.contentDocument.documentElement,"").getPropertyValue("width");
} else if (f.contentWindow) {
h = f.contentWindow.document.body.scrollHeight + 5 + "px";
} else {
return;
}
f.setAttribute("height",h);
f.parentNode.setAttribute("height",h);
}
if (window.addEventListener) {
f.onload = resize;
} else if (f.attachEvent) {
f.attachEvent("onload", resize);
} else {
return;
}
resize(); //starts resize function that was coded further up the code
}
//]]>
</script>
<iframe name="mainframe" id="mainframe" src="home.html" width="100%" frameborder="0" allowtransparency="yes" scrolling="No"></iframe>
É este o código que o site que indicaste utiliza, só tens de adaptar ao que tu queres
Qualquer dúvida é só perguntares