To assure that your optical mouse runs smoothly and verify that the motion of the pointer on the screen mimics that of the mouse, it is essential that the mouse is used on a dark, non-reflective surface. Otherwise, if the mouse is used on a bright, reflective surface, it will have trouble tracking its movement and the pointer on your screen will jump all around (or not even move at all). Furthermore, if a hair or excessive amount of dust is caught inside (through the opening in the bottom) your optical mouse, the pointer has a greater chance of randomly jumping around across the screen.