[javascript] Creating an IFRAME using JavaScript

It is better to process HTML as a template than to build nodes via JavaScript (HTML is not XML after all.) You can keep your IFRAME's HTML syntax clean by using a template and then appending the template's contents into another DIV.

<div id="placeholder"></div>

<script id="iframeTemplate" type="text/html">
    <iframe src="...">
        <!-- replace this line with alternate content -->
    </iframe>
</script>

<script type="text/javascript">
var element,
    html,
    template;

element = document.getElementById("placeholder");
template = document.getElementById("iframeTemplate");
html = template.innerHTML;

element.innerHTML = html;
</script>