Are you sure that note isn't coming from your BROWSER? Warning you that the security
certificate for that WEB SITE is invalid?
Typically you'd get a red background in the URL bar at the same time, depending on brower.
When some novice
upgrades too many things on a web site and doesn't understand their security certificate must ALSO be updated...that can happen. Or it the site owner asks for the certificate to be cancelled, because they lost
the password or their admin quit, that can happen.
Or when some malware host has taken over the web site or is impersonating it, and the web site has now been hijacked and may contain malicious code....
THAT'S when you don't want to connect to any web site that says "CERTIFICATE INVALID".
Call 'em up, send 'em an email
, if they can't fix it within a week? Avoid it like the plague, it means they have no grasp on security and your computer is at risk.