invalid security certificate

Using Firefox 56.0 (32-bit) to visit … f=6&t=3923
I get:

 Under Tools -> Page Info -> Security, it says:  
 I've been using this browser to visit vassalengine pages.  In particular, I get no warning on *this* page.

I’m sorry, the issue seems to be that Google chose to specify “https://” on some links. Changing it to “http://”, the page displays fine.