hello, please see [[Firefox no longer works with Mac OS X 10.5]]

Current Firefox versions need OS X 10.6 or later. * https://support.mozilla.org/kb/firefox-no-longer-works-mac-os-x-10-5 Firefox 16.0.2 is the last version that works on an Intel Mac with the OS X 10.5 operating system. * https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/16.0.2/mac/ Another option to consider is to install the last Firefox 10.0.x ESR version as that version is more recent than the Firefox 16.0.2 version. * https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/10.0.12esr/ * http://www.mozilla.org/en-US/firefox/10.0.12/system-requirements/ Firefox 17.0.x ESR has replaced the Firefox 10 ESR version, so you don't update.

If you can update to OSX 10.6 (can be cheap) then that is a good option also.

I am running OS 10.8.4 with an Intel Core i3. This is really too old? Also FF 23.0.1