If you are having issues with twitter feed showing in IE then this fixed it for me. Showed fine in FF, Chrome before this fix.
Add after the opening HTML tag.
Otherwise if the parent page forces IE9 to render in IE8 document mode, it forces all iframes to use the same mode which breaks HTML5 games (since IE8 doesn’t support HTML5). C2’s exported HTML uses that tag but it’s overridden if placed in an iframe.