Here is a simple script to quickly get an overview of the SSL certificates used on various websites,
e.g. to check expiration or issuer.
For me, this helped a lot while migrating website certificates to Let’s Encrypt.
While being quite happy with my new Firefox OS phone so far, the biggest stopper for me
was that, like all Mozilla products, the root certificate of CAcert was not included
and so I could not access sites using certificates assured by CAcert.