Firefox : Tips : Profile
From MozillaZine Knowledge Base
Your profile is stored in a folder named default/xxxxxxxx.slt where default is the name of your profile and xxxxxxxx are random numbers (for privacy)
On Windows XP, this can be found under:
C:\Documents and Settings\Your Name\Application Data\Phoenix\Profiles\
Note: The Application Data folder is "hidden" by default on Windows 2k/XP; you need to either set your computer to view hidden files (in Control Panel->Folder Options->View->Show Hidden Folders, or go to Start->Run->%AppData%
On Windows 98 and ME, this is found under:
C:\Windows\Application Data\Phoenix\Profiles\
On Mac OS X, this is found under:
/Users/Your Name/Library/Phoenix/Profiles/
On Linux, it is found in .phoenix in your home directory.
You can change the location of your profile, or create additional profiles, by executing Firefox with: firefox.exe -p