If you Allow push notifications, then this is why you see them appear on your desktop. The reason you’re even seeing these alerts in the first place is because you likely agreed to allow a website to send you push notifications at one time or another. If you miss a push notification, you can go back and review in the Notification Center. We talked at length about the Notification Center in an earlier article, so we recommend you read that if you want to know more about it. When you click on the Notification Center icon in the upper-right corner of the OS X desktop, you can see a history of these website notifications, just in case you missed any and, of course, you can remove them one by one if you prefer. Push notifications will appear as banners, which slide out from the top-right edge of the screen.