Unlike left-click and right-click, there is no standard for what the middle mouse button does. In some programs such as Microsoft Word and Excel, a single middle-click turns on Auto Scroll, letting you move your mouse to scroll without moving your finger. Another middle-click turns off Auto Scroll. In many applications, middle-clicking does nothing.
Tip: You can use the IntelliPoint Mouse software to reassign the middle button to another action. You can also assign the middle button to “disabled” if you don’t want to use it.