firefox v31.4.0 how do I make the default browser

it would be under menu>preferences>general , not under advanced.

Have a great day!

-Jon

Type about:preferences#general<enter> in the address bar. Turn on Always Check Firefox Default Browser.

This may have been disabled if you use a Firefox version from the repositories.

Try the version from the official Mozilla server if you currently use a version from the repositories of your Linux distribution.

You can find the full version of the current Firefox 31 ESR release in all languages and for all Operating Systems here:

• https://www.mozilla.org/en-US/firefox/organizations/all/

• https://www.mozilla.org/en-US/firefox/31.4.0/releasenotes/
• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/