Like the thread title says, the forum's layout is messed up in Firefox (61.0.1, Windows 10) due to mixed content restrictions. After going through the usual song and dance of clearing my cache, the problem remained. Looking at the source code, it seems that all of the CSS files are referenced with relative paths, and that the base HTML element has a URL of http://sonsofsamhorn.net rather than httpS://sonsofsamhorn.net. Dunno if that's the actual cause, but given what's happening on my end, and the message Firefox is giving me, it's at least a place to look.
What I'm currently seeing:
What I'm currently seeing: