1. A portable electronic device, comprising: a touch-sensitive display, the touch-sensitive display configured to separately display a plurality of user interface screens, including a first predefined user interface screen and a second predefined user interface screen; one or more processors; memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for: displaying a third user interface screen in the plurality of user interface screens, the third user interface screen being other than the first predefined user interface screen and the second predefined user interface screen; detecting a finger gesture on the touch-sensitive display while displaying the third user interface screen; and in response to detecting the finger gesture on the touch-sensitive display: replacing display of the third user interface screen with display of the first predefined user interface screen when the detected finger gesture is a first finger gesture; and replacing display of the third user interface screen with display of the second predefined user interface screen when the detected finger gesture is a second finger gesture that is a reverse of the first finger gesture.