"Mozilla’s change of policy revolves around this
notification. Whereas it used to say “we’re not sure
about this but you can accept if you want” — and most
users blindly accepted it anyway, it now says “We can’t
guarantee this and that might be because the server is doing
something nasty, please jump through this hoop to proceed
anyway” at which most users will be justifiably concerned and
not proceed. I’ve paraphrased there but the essence is
correct."