Firefox 4 versions and later do not run on a PowerPC Mac. Firefox 4 and later require at least OS X 10.5 and an Intel Mac. http://www.mozilla.org/en-US/firefox/8.0/system-requirements/ Firefox 3.6.24 (Mac OS X 10.4 and later) can be found here: http://www.mozilla.com/en-US/firefox/all-older.html (You allreaday have it) read the-edmeister reply here too: https://support.mozilla.com/en-US/questions/896057 (A group of Mac users have created their own Community Build from the "Firefox 4+" versions. TenFourFox for PowerPC's running Mac 10.4.11 & 10.5.8 . http://www.floodgap.com/software/tenfourfox/ http://tenfourfox.blogspot.com/ ) thank you Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.