It sounds that you removed the actual Firefox profile folder, but missed the profiles.ini file. This file registers all profile folders and if Firefox can't find the profile folder that is listed in this file then you get this error. You need to locate the profiles.ini file and delete this file or use the Profile Manager to create a new profile.

See:

• https://support.mozilla.org/kb/how-run-firefox-when-profile-missing-inaccessible

You can use one of these to make Firefox create a new default profile or recover an existing profile:

• delete the profiles.ini file to make Firefox create a new (default) profile
• use the Profile Manager to create a new profile
  If you still have an existing profile then click "Choose Folder" in the Profile Manager and browse to the location of a lost profile to recover this profile
  https://support.mozilla.org/kb/Managing+profiles

You should find the profiles.ini file in this hidden location:

• Mac: *~/Library/Application Support/Firefox/

If clearing the profiles.ini file isn't working then also check the location of the cache files.

• Mac: *~/Library/Caches/Firefox/Profiles/

You can also try to rename/delete the Mozilla\Firefox\ folder in both above mentioned locations (main, cache).

• http://kb.mozillazine.org/Profile_Manager
• https://support.mozilla.org/kb/Managing+profiles
• http://kb.mozillazine.org/Profile_folder_-_Firefox

All the Firefox folders and their contents (including profiles.ini) were deleted. I tired to do a clean re-install but it didn't work. Thanks

Did you try to use the Profile Manager to create a new profile?

• https://support.mozilla.org/kb/Managing+profiles

See also "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

I don't have Profile Manager on my computer. All the Firefox files were deleted. Since I deleted all the Firefox files, including the profile files, won't Firefox create a new profile folder when it opens? Thanks

Try to remove both locations that Firefox uses for the profile folder.

• ~/Library/Application Support/Firefox/
• ~/Library/Caches/Firefox

In Mac OS X v10.7 and later, the ~/Library folder is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X