The server's security certificate has expired
 

Or something like that is a message I seem to be getting very frequently lately.

Offered with "Accept" or "Reject" I wonder, should I really be bothered? It's come up on small websites and multinational companies.

Check your time and date are set correctly.

Done daily.

which websites?
if its the same one, maybe the cert has expired or been withdrawn

However the date issue would be my first place to look as well

I get some errors on website certificates where they are blocked by OpenDNS (e.g. 2o7.net), but they are not Expiry errors.

SD

The only site I can recall immediately was British Gas. Again from memory I think it may have always been on https sites.

yep, usually on https sites. Down to those that maintain them not renewing the certs when they should. Used to be 1 of my jobs where I used to work :)
Muppets probably don't diary the expiry dates.

ONLY on https sites! Certificates are not required for non-secure (http) pages.

SD

we used to use them on our internal domains for http sites so that they mimiced what were https site in production. Just saved the hassle of setting up https stuff