For some reason, my Fairphone doesn’t seem to accept the SSL security certificate of this forum. I’ve tried with both the built-in Android Browser and Google Chrome. The built-in browser warns that the certificate is invalid, but allows me to continue. Google Chrome simply blocks the way and doesn’t let me continue. I haven’t tried other browsers on my phone yet. Both Google Chrome and Firefox on my desktop computer accept the certificate without problems.
Maybe it has something to do with a missing intermediate certificate, as described in the answer to this Stackoverflow question.