Beginning with Firefox 4, Macs must have an Intel x86 processor (which you do have) '''''<u>and</u>''''' OSX 10.5 or higher (you have version 10.4) *System Requirements: [https://www.mozilla.org/en-US/firefox/4.0/system-requirements/index.html Firefox 4] [https://www.mozilla.org/en-US/firefox/5.0/system-requirements/index.html Firefox 5] [https://www.mozilla.org/en-US/firefox/6.0/system-requirements/index.html Firefox 6] [https://www.mozilla.org/en-US/firefox/7.0/system-requirements/index.html Firefox 7] [https://www.mozilla.org/en-US/firefox/8.0/system-requirements/index.html Firefox 8] If you upgrade your OS to 10.5 or greater, you can use the current Firefox version. '''''The good news''''' is that Firefox 3.6.24 still supports OSX 10.4 and Macs with the PPC Mac architecture. '''''The bad news''''' is that support for the Firefox 3.6.x series is likely to end in the first quarter of 2012. *System requirements: [https://www.mozilla.org/en-US/firefox/3.6/system-requirements/index.html Firefox 3.6.x] *Download Firefox 3.6.24: https://www.mozilla.org/en-US/firefox/all-older.html *Also see --> http://support.mozilla.com/en-US/kb/Installing+Firefox+on+Mac '''''EDIT''''': SafeBrowser deleted information re: TenFourFox; not an applicable solution for this user who has an Intel processor. '''If this reply solves your problem, please click "Solved It" next to this reply when <u>signed-in</u> to the forum.'''

The OP dsternberg has an Intel Mac according to the Safari user agent, so TenFourFox won't run on that computer and the only option is to install Firefox 3.6.x or update to OS X 10.5 if possible. *Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_4_11; en)