When creating an iframe, at what point does the iframe's contentWindow property become available? Is it only assured after the onload event is fired? Is it available immediately after inserting the iframe into the DOM? The test below can be run to detect the availability point for different browsers.
| Google Chrome (53.0.2785.116) | At DOM Insertion Time |
| Mozilla Firefox (49.0.1) | At DOM Insertion Time |
| Opera (40.0.2308.75) | At DOM Insertion Time |
| Apple Safari (9.1.3 (11601.7.8)) | At DOM Insertion Time |
| Microsoft Edge | At DOM Insertion Time |
| Internet Explorer 11 | At DOM Insertion Time |
| Internet Explorer 10 | At DOM Insertion Time |
| Internet Explorer 9 | At DOM Insertion Time |
| Internet Explorer 8 |
At DOM Insertion Time
contentWindow access before appendChild causes "Unspecified error" |
| Internet Explorer 7 |
At DOM Insertion Time
contentWindow access before appendChild causes "Unspecified error" |
| Internet Explorer 6 |
At DOM Insertion Time
contentWindow access before appendChild causes "Unspecified error" |