1. A method to control a computer generated presentation on a display screen, wherein the presentation includes displaying multiple screen images in a presentation order at one or more different locations and at one or more different zoom levels on a canvas within a zooming user interface and wherein the presentation includes displaying panning and zooming between the screen images, the method comprising: displaying on the display screen at least a portion of the presentation; in response to user input adding an indication of a new screen image to the displayed portion of the presentation, displaying on the display screen a new thumbnail image that corresponds to the new screen image and displaying on the display screen an animation that moves in between the new screen image and the new thumbnail image to indicate on the display screen a correspondence between the new thumbnail image and the new screen image.