I was using FreeMind to manage information of my work, and there were several links embedded in the mind map. When I was trying to open the links, they were opened in Firefox instead of Chromium that has been my default browser. I tried to set Chromium as the default browser in the Preferences tab but it said ``Chromium cannot determine or set the default browser.''
Ubuntu Forums. In the thread, user cavalier911 provided a method using update-alternatives to set the default browser. The command is as follows.
$ sudo update-alternatives --config x-www-browser
Pretty easy and works like a charm.