If you have seen security certificate error when open any website these are three cause :-
computer date is wrong or certificate has really expire or web site is not trusted.
when seen this error to check computer date and time setting.Suppose computer
date and time are not set means it’s resetting again and again then check
computer cmos battery.
After set date not see this error again but suppose this error seen again means
this site certificate is really expire or this site is not trusted.