Non-sensical mixed content message

I'm using Fiddler to look at the page elements. I just checked the Javascript now, and there's nothing in there that's making an external call.

 

 

I didn't mention that I can load exactly the same page on my test server (not behind an F5) and get no mixed content messages at all. It's almost like there's something in the HTTP request or response headers that's specific to the F5 but has no bearing on the actual content of the page.

 

 

Gary