Is that even actually possible? I’ve half a memory that cross-site iframes are explicitly blocked in browsers to prevent malicious code.
EDIT: seems so, looking at that page. Live & learn.
You can have them but normally the JS etc cannot interact with the parent or other iframes on the page.
Can I also add a request for gifv format? I think they just need to use the HTML5 video tag. GIFs from supported sites (e.g. gfycat, imgur etc) will be then 1MB instead of 25MB.
I don’t know what forum software this is, but if it’s a customised off-the-shelf thingy then there’s probably a plugin already written.