Your connection is not secure
Here: http://i.imgur.com/SNoQvBZ.png
I don't use any kind of antiviruses or firewalls. Windows Firewall is turned off manually in group policy, registry, services and files are deleted. Same applies to Windows Defender. I don't have any viruses, PC is completely clean. Same applies to UAC and all other crapware of Microsoft(Windows 10 start, Windows 10 apps, Metro, Cortana, Telemetry, etc., etc., etc...)
What I want is to turn this message off completely not only for this website but completely for all websites, even if website will set my computer on fire if I try access it. And I don't care if it will decrease security of my PC(or whatever), I want to turn it off.
Is there a way to turn it off completely? Because all I find on the internet is something like this: https://support.mozilla.org/en-US/questions/1104863
ყველა პასუხი (2)
No, Firefox does not have a blanket setting to ignore certificate invalidity on all sites.
In this particular case, you can see the site let its certificate expire. If you want to use the site anyway, you can click the Add Exception button to bypass the problem. I suggest unchecking the box for making a permanent exception since they are likely to get a new cert soon.
A simple cause can be due to the date/time being incorrect on the OS.