RPI3 and firefox... in case it helps - by: maudy

In case this helps others, that occasionally need to use firefox on their RPI3 and also keep the RPI3 up to date...

Typically after running:

$ sudo apt-get update
$ sudo apt-get dist-upgrade

firefox stops working for me.

Jasem helped me out with these lines and it gets firefox working again:
$ wget ports.ubuntu.com/pool/main/f/firefox/fir...u0.12.04.1_armhf.deb
$ sudo apt-get purge firefox
$ sudo dpkg -i firefox_52.0.2+build1-0ubuntu0.12.04.1_armhf.deb

Adding this line will also allow you to hold firefox at this working version:

$ sudo apt-mark hold firefox

Should you later want to update firefox then:

$ sudo apt-mark untold firefox

I hope this helps others.