Certificate manager

I don’t recall which web site but it has HTTPS & i clicked on it & i received an error “secure connection failed”.

So i did some research & found it might have something to do with Certificate manager.Out of curiosity i looked at it.Not sure what it is for or what to do with it.In the right column are dates that are expired,such as yahoo,google & some i have no idea what they are.

Is it safe to delete the one’s that are expired.Also am i supposed to do anything with this certificate manager on occasion.