How do I get rid of the constantly appearing pop up: Safari can’t verify the identity of the website… Would you like to connect to the website anyway?

I would like to get rid of the frequent pop-up on my iMac desktop.

“Safari can’t verify the identity of the website ...

This certificate for this website is invalid. You might be connecting to a website that is pretending to be…, Which could put your confidential information at risk. Would you like to connect to the website anyway?”

The options given below this message are: Show certificate, Cancel or Continue.

This pop-up is reoccurring every time I change the page, with the only difference being the change in web address . How do I make it stop?