Bellow is how to fix Error This Connection is Untrusted in FireFox after installed Kaspersky Internet Security 2015.
you have asked firefox to connect securely to account.google.com, but we can’t confirm that your connection is secure.
Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site’s identity can’t be verified.
If you usually connect to this site without problems, thie error couild mean that someone is trying to impersonate the site, and you shoulldn’t continue.
I can not access Gmail, Google plus and other Google services using Firefox. I have tried a lot of different ways, such as reset FireFox, disable Kaspersky Adsvisor but it’s not working for me. After about 30 minutes I figured out how to fix “Error This Connection is Untrusted” error.
1. In your computer, go to: C:\ProgramData\Kaspersky Lab\AVP15.0.1\Data\Cert , you will see a file name (fake)Kaspersky Anti-Virus Personal Root Certificate.
Note: ProgramData often set hidden so you must show hidden files if you want see this folder
2. Open FireFox
– Tools ==> Options ==> Certificates ==> View Certificate
– Select Authorities Tab and click to Import button
– Browse to (fake)Kaspersky Anti-Virus Personal Root Certificate file and import it.
3. Close and then open FireFox again! Done !
Sometimes this problem by: Current date time, so you just need correct it
I hope this article can help you fix this error when you get it.