I'm having a strange issue where I try to insert an iframe into the HTML view on a secondary html content block, and it is stripped out when I update it.
Here's the html minus the correct youtube video code...
<iframe title="YouTube video player" class="youtube-player" type="text/html" width="567" height="455" src="http://www.youtube.com/embed/xxx?rel=0" frameborder="0" allowFullScreen></iframe>
I tried replacing the double quotes with single quotes.
Another issue that might be related is that I've had to add the media buttons myself with an appropriate hook as they never showed up when I checked 'show media buttons' in the secondary html content configuration settins.