All notifications created for you by the platform or any of the webapps on it are accessible in the “Notifications” webapp. Access the webapp either by clicking the notifications icon in the main menu bar or in the app menu.
All outstanding notifications are displayed in the Tasks list. To dismiss a notification, simply click the check box alongside it, a line will be placed through the notification. To update the list after you have marked all notifications as complete, simply reload the page.
If you have marked a notification as read but have not yet reloaded the page, you can reopen the notification by removing the tick from the check box. Just click the check box again to remove the tick.