You can get an installer for Firefox 3.6 here: http://www.mozilla.com/firefox/all-older

I recommend first backing up your Firefox settings in case something goes wrong. See Backing up your information (copy whole profile folder)

thanks for your response. All my settings are gone along with the old version.

I went to the link you supplied, "backing up profile without opening firefox. But there is no info for Macs. It would be nice to knowhow to find it, since Firefox is one of only two search engines useable...

I found Mac in the right sidebar. Hopefully this link will work: https://support.mozilla.com/en-US/kb/Backing%20up%20your%20information#os=mac&browser=fx35

Firefox 4 requires at least OS X 10.5 and an Intel Mac.

• http://www.mozilla.com/firefox/4.0/system-requirements/

For an unofficial Firefox 4 compatible version that runs on Mac OS X 10.4.11 or Mac OS X 10.5.8 (PowerPC) you can look at:

• http://www.floodgap.com/software/tenfourfox/

Firefox 3.6.x (Mac OS X 10.4 and later) can be found here:

• http://www.mozilla.com/en-US/firefox/all-older.html