1. A computer-implemented method, comprising: at a portable multifunction device with a touch screen display: displaying a first user interface without concurrently displaying a second user interface that is distinct from the first user interface; detecting a gesture on the touch screen display to select the second user interface; and in response to detecting the gesture, displaying an animation of a transition from display of the first user interface to display of the second user interface, the animation comprising sliding a first element of the second user interface onto the display from a first side of the display while simultaneously sliding a second element of the second user interface that contacts the first element horizontally across the top of the first element, wherein the first element of the second user interface is distinct from the second element of the second user interface.