Updated App Store Review Guidelines by Apple…
The app approval process is in place to ensure that applications are reliable, perform as expected, and are free of explicit and offensive material. We review every app on the App Store based on a set of technical, content, and design criteria. This review criteria is now available to you in the App Store Review Guidelines. These guidelines are designed to help you prepare your iOS and Mac OS X apps for the approval process.
via App Store Review Guidelines – App Store Resource Center.