web pages rejected for bad certificate

surf to an example web page. click on the lock icon in the address bar, or if a message comes up, ask to see the certificate chain. This site as an example:

Certificate will be less baffling if you take a look at them from time-to-time, such as by clicking on the one for the Apple forums in your browser (not in an email, if that is how you are reading the responses).

Other common reasons for not opening a page are 'too many redirects' where one site forwards to another and another too many times.

If you type a web site NAME as the URL, the certificate MUST reference that web-site name, else It fails to be seen as valid and you get blocked and 'you may not be connecting to the web site you expected' messages. This is what you want to have happen, so that when you say "Apple" it goes to the genuine Apple, not something similar but not quite right.

what version MacOS?

has the battery been allowed to run down to Zero recently? is the date & time correct within five minutes?