How to upgrade to iOS 8 (and downgrade to iOS 7 if you regret it)
The limited path back
Because it comes as a surprise to a lot of people, it’s important to know the following from the get-go: Once you update your device to iOS 8 there’s very little chance that you’ll be able to revert to a previous version. Apple stops “signing” (authorizing) older versions of iOS just days after releasing a new one. Reverting during this brief window is possible (and we’ll explain how at the end of this story). But once that window closes, there’s no going back.
from Macworld http://ift.tt/XCN8Tm