How do I remove notifications from certain websites not in my Chrome or Safari browsers? I am getting notifications from sites I have visited in the past such as SitePoint. I have gone to the Chrome extensions and I do not see it there and I checked out my MacBook notifications, nothing there regarding these sites and yes I have also checked out the Internet Accounts, nothing there either.

How do I stop receiving those annoying notifications from these vendors?

I don't mind the alerts, I just want to end them for some particular vendors.
Go to safari preferences and then in websites tab. Second last in the list is notifications. Edit whichever you want. 

Might have similar for chrome. I don’t use it so don’t know. 

In Firefox, searching settings for permissions gives me the option.