For some reason, Firefox will occasionally block sites that I try to enter, including google.com, with a message that says 'Insecure Connection'. There is no way for me to override this, and adding an exception does not solve the issue. The connection most certainly IS secure, so I don't know why Firefox is doing this. I do not have any antivirus software. This started happening when I switched from Windows 10 to Ubuntu, and also now on Linux Mint.