Dave Ward says,
It’s not exactly light reading, but section 4.2 of RFC 3986 provides for fully qualified URLs that omit protocol (the HTTP or HTTPS) altogether. When a URL’s protocol is omitted, the browser uses the underlying document’s protocol instead.
Put simply, these “protocol-less” URLs allow a reference like this to work in every browser you’ll try it in:
//ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js
It looks strange at first, but this “protocol-less” URL is the best way to reference third party content that’s available via both HTTP and HTTPS.
This would certainly solve a bunch of mixed-content errors we’re seeing on HTTP pages — assuming that our assets are available via both HTTP and HTTPS.
Is this completely cross-browser compatible? Are there any other caveats?