Firefox : Tips : Profile
From MozillaZine Knowledge Base
Your profile is stored in a folder named default/xxxxxxxx.slt where xxxxxxxx are random numbers (for privacy)
On Windows XP, this can be found under:
C:\Documents and Settings\Your Name\Application Data\Phoenix\Profiles\
On Windows 98 and ME, this is found under:
C:\Windows\Application Data\Phoenix\Profiles\
On Linux, it is found in .phoenix in your home directory.
You can change the location of your profile by executing Firefox with:
MozillaFirefox.exe -p