Who knows, I tend to send http links and https links as http or www.

The mozilla stuff check for valid certs.

But if its expired or if its not got one ie its just an http link even with the https everywherething which is technically supposed to handle that transaction for us, sadly it choaks if the cert or something is out of whack.

Its easier but probably less secure ignoring certs all together or simply never using https yourself.

If you don't chances are it will find it if it is and if it isn't it will not complain.

It seems in all mozilla stuff if you use https from a user point of view it screws you over.

If you don't and if there is the system is fine if it it does that itself.

Saying that on some hardware manufacturers like router and my printer they say that when entering https mode on the hardware that you will get a message that the site is unsafe probably because it doesn't have a cert as such and to say its safe to bypass.