Install Firefox on Debian 8
Updated at: 10/03/2017

Per "installare" la versione vera di firefox su Debian 8 nel mentre che decidono se aggiornare i pacchetti nel repository, si può fare nel seguente modo:
  • Download latest Firefox from: http://www.mozilla.com . If using wget, remember to escape any & with \ so it doesn't break the url down into a series of background process
  • Copy the downloaded file to /opt
  • Extract it using: 
    $ tar -jxvf firefox-x.x.xx.tar.bz2
  • Create a symbolic link 
    $ sudo ln -s /opt/firefox/firefox /usr/bin/firefox
  • if the file alreasy exists: 
    $ sudo mv /usr/bin/firefox /usr/bin/firefox-esr
    $ sudo ln -s /opt/firefox/firefox /usr/bin/firefox
  • Delete firefox-x.x.xx.tar.bz2 from /opt
To install new versions, you are supposed to 
# rm -rf /opt/firefox*
# rm /usr/bin/firefox
To make a desktop icon, do this 
$ sudo touch /usr/share/applications/firefox.desktop
Edit this using your favourite text editor: 
$ sudo nano /usr/share/applications/firefox.desktop
Contents of firefox.desktop: 
[Desktop Entry]
Encoding=UTF-8
Name=Firefox
Comment=Browse the World Wide Web
GenericName=Browser
Terminal=false
Exec=/usr/bin/firefox %U
Icon=/opt/firefox/browser/icons/mozicon128.png
Type=Application
StartupNotify=true
Categories=Network;WebBrowser;
Keywords=firefox;
  Source: https://superuser.com/a/322381