For some reason Web Browsers such as Safari have added the ability for Web Sites to request the sending of Notifications using the OS notification system. Quite why anyone would want this on 99% of the sites is beyond me.
If you are fed up with constantly having to say no to these requests there is a way to turn off all requests in Safari, and certainly other browsers too.
To turn of the prompts go to:
Settings > Websites > Notifications
and deselect the check box at the bottom of the pane.