The owner of fafafaf.bitbucket.org has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.
There is something else with that website as well. Until a couple of days ago, I could see the playing statistics of the players by typing in the replayID. Now nothing happens if I do that.