1. Click the Firefox Menu.

Click Firefox menu

2. Select and open “Options”.

Select Options

3. Select the “Advanced” option and then the “Certificates” tab…

Select Advanced options and Certificates tab

…then click View Certificates.

Click View Certificates

4. In the “Certificate Manager” panel, click the “Authorities” tab and select the target certificate, then click the Delete or Distrust button.

Authorities tab

5 .  In the “Delete or Distrust CA Certificates” panel, make sure the target certificate is the one you wish to delete, then click OK to remove it.

Delete or Distrust CA Certificates