PH insecure?

[AW111]

I am getting browser security warnings every couple of pages, using Opera (from Australia).

Normal page:







Insecure : note no padlock icon in address bar:







When I click on the i icon:


I'm on my phone at home, so don't have any tools to diagnose further.

[AW111]

The interesting thing is that the "insecure" pages are https, and I'm not getting any warnings about invalid certificates, so what don't the browsers like about it?