Microsoft Windows XP

 

C:\Documents and Settings\{user}\Application Data\Mozilla\Firefox\Profiles\{profile folder}\
C:\Documents and Settings\{user}\Local Settings\Application Data\Mozilla\Firefox\Profiles\{profile folder}\Cache\

Microsoft Windows Vista / 7

 

C:\Users\{user}\AppData\Roaming\Mozilla\Firefox\Profiles\{profile folder}\
C:\Users\{user}\AppData\Local\Mozilla\Firefox\Profiles\{profile folder}\Cache\

Apple Macintosh OS X 10.6

 

/Users/{user}/Library/Application Support/Firefox/Profiles/{profile folder}/
/Users/{user}/Library/Caches/Firefox/Profiles/{profile folder}/Cache/