[javascript] Creating an IFRAME using JavaScript

You can use:

<script type="text/javascript">
    function prepareFrame() {
        var ifrm = document.createElement("iframe");
        ifrm.setAttribute("src", "http://google.com/");
        ifrm.style.width = "640px";
        ifrm.style.height = "480px";
        document.body.appendChild(ifrm);
    }
</script> 

also check basics of the iFrame element