I think IE8 did something like this, w.r.t content not served over https during an https session. It was a yes/no box worded like "Do you want to view the conte

I think IE8 did something like this, w.r.t content not served over https during an https session. It was a yes/no box worded like "Do you want to view the content only served over https?" assuming the users would generally click "yes" thinking it was the more permissive option.