Get IFrame's document, from JavaScript in main document
You should be able to access the document in the IFRAME using the following code:
document.getElementById('myframe').contentWindow.document
However, you will not be able to do this if the page in the frame is loaded from a different domain (such as google.com). THis is because of the browser's Same Origin Policy.
The problem is that in IE (which is what I presume you're testing in), the <iframe> element has a document property that refers to the document containing the iframe, and this is getting used before the contentDocument or contentWindow.document properties. What you need is:
function GetDoc(x) {
return x.contentDocument || x.contentWindow.document;
}
Also, document.all is not available in all browsers and is non-standard. Use document.getElementById() instead.
In case you get a cross-domain error:
If you have control over the content of the iframe - that is, if it is merely loaded in a cross-origin setup such as on Amazon Mechanical Turk - you can circumvent this problem with the <body onload='my_func(my_arg)'> attribute for the inner html.
For example, for the inner html, use the this html parameter (yes - this is defined and it refers to the parent window of the inner body element):
<body onload='changeForm(this)'>
In the inner html :
function changeForm(window) {
console.log('inner window loaded: do whatever you want with the inner html');
window.document.getElementById('mturk_form').style.display = 'none';
</script>