I have been getting a passive mixed content warning on my FireFox. Essentially it means that the site is secure using HTTPS, but there are linked elements such as images from other sites that might not be secure.
From my perspective that's not really an issue. Passive mixed content can't really be used to steal personal data. I think it's more of a security risk in term of phishing/misleading.
EDIT: for example on this page it's Blaster's signature picture. Which comes from http://i.imgur.com/KshaBLB.gif , and that's why it's not secure. I don't get that warning on the main forum page.
It's good to know it isn't a threat. It is happening to me every time I try to click on the UFO thread on the OT board.
I get the same passive mixed content warning on that page. I only get a 301(HTTP status code) on Ozy_Flame's watch picture in his status. There are a couple of http links on the page as well(poll, and a signature link), but I doubt they would trigger your firewall.
