On my system, firefox's menus were too small to read. Here's a way to adjust them.
Create firefox chrome directory for root user:
susdo mkdir /root/.mozilla/firefox/pluto.default/chrome
Copy the example userChrome.css file from the linuxmce user account to the this directory:
sudo cp /home/linuxmce/.mozilla/firefox/*.default/chrome/userChrome-example.css /root/.mozilla/firefox/pluto.default/chrome/userChrome.css
Set ownership of the chrome directory and contents to root:root
sudo chown -R root:root /root/.mozilla/firefox/pluto.default/chrome
Edit /root/.mozilla/firefox/pluto.default/chrome/userChrome.css and add the following:
* {
font-size: 16pt !important
}
Adjust the font-size to whatever looks best on your system.
HTH,
Roy