A new beta of iPhone OS 2.2 was briefly posted last night as Apple released an updated iPhone developer NDA. However, from what we have heard from developers we know, the download wouldn't work was removed shortly after it was made available.
In iOS 5 the latest version of iOS operating system, you want to remove the notifications from your screen all you need is to swipe your finger towards left across the notification and that's all. This trick works because of briefly activating the notification center and letting it go, this causes the notification to dismiss