Firefox mixed content warning (HTTP image loaded on HTTPS)
Or this issue has been fixed or you're using an old cache, because I don't have this issue.
cc @JasonBarnabe
that warning is caused by this link within the page source
http://cdn.vanillaforums.com/images/usericon_50.png
that link can be changed to https but its ssl certificate is outdated and will cause a risk warning in firefox
Firefox mixed content warning (HTTP image loaded on HTTPS)
Please load the Vanilla Forums user icon from an HTTPS source. Firefox displays a mixed content warning in the address bar on all forum pages here, including the Sign In page.
It likely scares away novices who don't understand what it refers to. And as for those of us that do, it's such an eyesore to see that blemish because of a silly little image.