LittleGolem's HTTPS certificate has expired?

The certificate appears to have expired on February 12th, 2018, at 12:45 PM EST (which is about 10 minutes ago).

:(

I expect a lot of people who have the HTTPS version of the URL bookmarked won't know how to overcome this and will think the site is down. Not to mention tools that used the HTTPS URL to pull data (which they should be doing).

Yes, it has expired.  A certificate issued by Let's Encrypt is valid for 90 days.  The owner of the website is supposed to set up a cron job to renew the certificate periodically.

So how can you connect with Firefox which won't allow for a server exception as the site  uses HTTP Strict Transport Security (HSTS) ?

One way is to ask for its IP address (Whois or nslookup) and use that in your browser : http://188.166.30.209 and input your login and password.

Looks like Richard has fixed it already :)