Thanks for reporting this.

I can't quite understand what happened - the error says firefox did not continue because "this website requires a secure connection". Surely the fact that it is a secure connection is a good thing and not a reason to not connect.

I use https for the site and have tested with different browsers including firefox without successfully reproducing.

The example page is being blocked by hospital IT using something called "Cisco Umbrella" which on ancient internet explorer will redirect to display a warning saying that it's been blocked by "Cisco Umbrella", but on everything else the Cisco redirect is detected as MitM and you just get security warnings.

Honestly, I'm surprised fabhomepages itself wasn't blocked. I just thought it was odd that one would load and the other wouldn't. So basically what's happening is:

https://fabhomepages.com/ : whitelisted

https://luxury-villa.incostadelsol.com/ : blacklisted