Where does Firefox store cerificates and how to delete one?

Solution 1:

For newer FF go to Options > Privacy & Security > Certificates, there is a button View Certificates...

For older FF, if you go to Tools > Options > Advanced, there's a button in the bottom left labeled View Certificates. This will bring up the Certificate Manager. You can delete them from there.

Solution 2:

Firefox stores its certificates in the C:\Documents and Settings\< Windows login user name>\Application Data\Mozilla\Firefox\Profiles\< profile folder > . Remember that the Application Data folder is a hidden folder. Therefore, you need to open Windows Explorer and choose Tools → Folder Options → View (tab) → Show hidden files and folders

There is file named cert8.db in the default profile folder. You can use the Certificate Database tool (certutil.exe) command line tool to delete the certificate from the database.

certutil -D -n < certificate name >

You can obtain windows binaries of certutil.exe by downloading NSS and NSPR from Mozilla.

Unzip NSS and NSPR, then copy everything from both "bin" directories and both "lib" directory into a single location. Run certutil.exe from that location and point the tool to your cert8.db file with the "-d \path\to\profile\"

Example :

certutil.exe -D -n < certificate_name > -d "C:\Documents and Settings\Username\Application Data\Mozilla\Firefox\Profiles\4abcdefg.Guest\"

More information on certutil.exe can be found in Mozilla's documentation on certutil

Hope this helps you.