You need to set Firefox as your default browser. See Make Firefox your default browser

I have Firefox as my default browser already. It's just outside links that doesn't work. They open up with IE, even links that used to open up with Firefox just a week ago.

Try Links do not open in Firefox

Try to redo the default browser and make another browser like IE the default browser and then let Firefox do it again.

See http://kb.mozillazine.org/Default_browser and Setting Firefox as the default browser does not work - What to do

I use Firefox as my default browser on my iMac with Yahoo as my home page. The problem occurs when I try to open an embedded link in email or a shortcut - Firefox opens two links - my home page and the link I clicked on??? I also have Safari and Opera and neither one of them do this - is there a setting I missed that would overcome this - it is very frustrating to say the least!

See Bug 531552 – Firefox 3.6 opens two windows when opening external links

please do not comment in bug reports

Thanks to cor-el for the bug reference and after looking at the bug comments, I think someone is missing the boat because I am using Firefox 4.0b1 and the problem persists even in this beta version! And it didn't just start - it happened in the previous version of 3.6 and whatever iterations followed before 4.0. I can't tell by the techie comments in the bug reports if they have a clue or not - but since it has been reported and is still occurring in 4.0, I wonder????

I'm running an iMac with OS X 10.6.4 with 3 gb RAM on a 2.16 Intel core 2 duo processor. Is this a Mac issue because I don't have the same problem on my WIN XP machine??