How can I manually change the default web browser? [closed]

Run in a terminal:

sudo update-alternatives --config x-www-browser

The output should look like this:

There are 3 choices for the alternative x-www-browser (providing /usr/bin/x-www-browser).

  Selection    Path                       Priority   Status
------------------------------------------------------------
* 0            /usr/bin/epiphany-browser   85        auto mode
  1            /usr/bin/chromium-browser   40        manual mode
  2            /usr/bin/epiphany-browser   85        manual mode
  3            /usr/bin/firefox            40        manual mode

Press enter to keep the current choice[*], or type selection number: 3
update-alternatives: using /usr/bin/firefox to provide /usr/bin/x-www-browser (x-www-browser) in manual mode.

Choose what you want to set as default.

The software centre version of Firefox has Ubuntu Firefox Modifications to enable it to work and integrate with Ubuntu better. The linux version you can download from Mozilla direct does not have this add on so that is likely the reason why you cannot integrate it into the system as you wish.

I guess your option here is to live with what you have or try and install the Ubuntu version and troubleshoot the issues with it.

I had problem with mozillateam ppa for firefox-stable.

This will do the trick

sudo add-apt-repository ppa:mozillateam/firefox-next
sudo apt-get update
sudo apt-get install firefox # (even if you have `firefox` installed)  

You will have the latest version of Firefox which is currently v 10.

Then try System Settings → System Info → Default Applications. There change the Web. Firefox must be there this time.