Comment 4 for bug 1207140

I just had a discussion with Robert about this. The "//" URL is a standard (though somewhat obscure) way to write a URL. It's usually referred to as a "protocol-relative URL", it's part of the RFC definition for URLs, and it's supported by all the modern browsers including IE7+ (although apparently IE7 & 8 will attempt to fetch the http and https version a protocol-relative URL resource http://billpatrianakos.me/blog/2013/04/18/protocol-relative-urls/ )

Since Firefox 23 has just introduced a new default setting that blocks iframes which have a different http/https protocol than the parent page, I bet we're going to see many more vendors start adopting protocol-relative URLs in their embed code. So what we ought to do is adapt Mahara to handle these properly.

Although, for backwards-compatibility, we're also going to need to do a find/replace on all the existing external content blocks, to make sure their iframe URLs match up with the site's URL. That could either be a DB upgrade script, or it could be a last-minute find/replace in the external content block's rendering function.