My point is that while I may trust domain X, this does not mean I trust domain Y. (Maybe they are not malicious, but I consider their security measures to be sub-par.)

If domain X starts referencing material from domain Y within its secure pages, I would like to be aware of this. My understanding is that once such material is incorporated into the browser-constructed page representation, it has full access to that representation. If the inclusion is a component that has the ability to control the browser (e.g. a script), then that component can observe or manipulate the page and its activity.

That is one reason not to trust an https page that includes content references/retrieved via http; the latter is easily subjected to a man in the middle attack.

The technique described in the article avoids this point, but it doesn't describe what if any notice browsers provide to the user that a second, authenticated domain/certificate is involved in the current communication.

Maybe I'm incorrect in my understanding (I'm no expert in this, by any means). But this is what forms the basis of my question.

Edit: I'll leave my question as a testament to my over-tired, over-caffeinated rashness. I take your point now, more fully, that specifying a link having the protocol prefixed, as opposed to this, will produce the same result end in the browser.

So, I guess my question reduces to a "browser 101" question of what does happen under those circumstances, with regard to browser presentation. Which I really should be able to determine on my own, with a bit of googling and/or experimentation.

My apology for putting my typing ahead of more collected thought.

I haven't spent much time addressing this particular area. Most of my work has been more behind the scenes and in communications paths where trust is already established.