How Do I Disable Website Notifications In Safari?

Launch the Safari app on your Mac and go to Safari > Preferences (or press Command-Comma). Click on the Websites tab and select Notifications from the sidebar (in older versions of Safari the tab will be named Notifications instead of Websites).

Next you can manually disable/enable notifications from select sites, remove all notifications, or even prevent sites from asking permission to send push notifications. The changes should be effective as soon as you make them and it should not be necessary to restart the Safari browser.