Was not sure which forum this should go under so I've put here.
Some Forum pages display thus:-
Not a problem, just curious.
I'm using Firefox.
I've spotted that one as well. It appears to show a warning on any pages that pull in additional content that is not encrypted using HTTPS. It's a warning that parts of the page are not secure.
Having looked at what's included in each page, it seems that any thread that contains a post by john46 contains an image http://img01.bt.co.uk/s/assets/020615/images/background.jpg which is not from an encrypted server.
Ok, thanks Ectophile.