Beginning with Firefox 4, Macs must have an Intel x86 processor; your system is a PPC Mac. *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] '''''Note to everyone. Firefox 4 is no longer maintained or updated and contains known security issues that will not be fixed. Use it at your own risk. Beginning with Firefox 4, each new release thereafter, replaces the prior version and the prior version is abandoned as to updates. <u>As of this reply, 11-10-2011, Firefox 4 through Firefox 7.0.1 are no longer maintained or updated and all contain security or stability issues.</u>''''' The good news is that Firefox 3.6.24 (which you have installed) still supports 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 You can try the third-party product '''''TenFourFox''''' that supports PPC Macs. Firefox 8 version of '''''TenFourFox''''' is available. The product is based on Firefox released versions. All support is provided by the developer, not by this site: *Home page: http://www.floodgap.com/software/tenfourfox/ *Developer's blog: http://tenfourfox.blogspot.com/ '''If this reply solves your problem, please click "Solved It" next to this reply when <u>signed-in</u> to the forum.''' ------------------------- Not related to your question, but... You may need to update some plug-ins. Check your plug-ins and update as necessary: *Plug-in check --> http://www.mozilla.org/en-US/plugincheck/ *Adobe Shockwave for Director Netscape plug-in: [https://support.mozilla.com/en-US/kb/Using%20the%20Shockwave%20plugin%20with%20Firefox#w_installing-shockwave Installing ('''''or Updating''''') the Shockwave plugin with Firefox] *Adobe PDF Plug-In For Firefox and Netscape: [https://support.mozilla.com/en-US/kb/Using%20the%20Adobe%20Reader%20plugin%20with%20Firefox#w_installing-and-updating-adobe-reader Installing/Updating Adobe Reader in Firefox] *Shockwave Flash (Adobe Flash or Flash): [https://support.mozilla.com/en-US/kb/Managing%20the%20Flash%20plugin#w_updating-flash Updating Flash in Firefox] *Next Generation Java Plug-in for Mozilla browsers: [https://support.mozilla.com/en-US/kb/Using%20the%20Java%20plugin%20with%20Firefox#w_installing-or-updating-java Installing or Updating Java in Firefox]