iframe element in a wml document at runtime

Hello! I want to use an iframe element in a wml document. I know that iframe it's not supported in a wml document, but Opera doesn't care about it and it can use it and I don't care about other browsers . The problem is that I can't make the iframe work if I add it dynamically.

In Opera the iframe works if I have this:

<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>
    <card id="main" title="Title">
        <p>some text</p>
        <iframe src="http://site.com"></iframe>
    </card>
</wml>

Code (markup):

But if I try to add the iframe at runtime with javacript it doesn't wok:

var iframe = document.createElement('iframe');
iframe.setAttribute('src','http://site.com');
iframe.setAttribute('width','200');
iframe.setAttribute('height','200');

var card = document.getElementsByTagName('card').item(0);
card.appendChild(iframe);

Code (markup):

The iframe it's added (checked the generated source with opera dragon fly) but it's not displayed!

Is there a way to make this work?

Thanks for your time, have a nice day!