In computing, a mouse gesture is a way of combining computer mouse movements and clicks which the software recognizes as a specific command. Mouse gestures can provide quick access to common functions of a program. They can also be useful for people who have difficulties typing on a keyboard. For example, in a web browser, the user could navigate to the previously viewed page by pressing the right mouse button, moving the mouse briefly to the left, then releasing the button.The first mouse gesture, the “drag,” was introduced by Apple to replace a dedicated “move” button on mice shipped with its Macintosh and Lisa computers. Dragging involves holding down a mouse button while moving the mouse; the software interprets this as an action distinct from separate clicking and moving behaviors. Although this behavior has been adopted in a huge variety of software packages, few other gestures have been as successful. As of 2005, most programs do not support gestures other than the drag operation. Each program that recognizes mouse gestures does so in its own way, sometimes allowing for very short mouse movement distances to be recognized as gestures, and sometimes requiring very precise emulation of a certain movement pattern (e.g. circle). Some implementations allow users to customize these factors.The Opera web browser has recognized mouse gestures since version 5.11 (April 2001). Several mouse gesture extensions are also available for the Mozilla Firefox browser, such as the Optimoz Mouse Gestures extension that offer also Rocker gestures performed by pressing one mouse button while holding down the other (this offers two additional commands, usually moving forward/backward). These extensions use almost identical gestures as Opera.