If you find it is becoming difficult to target areas on your screen, you may need to clean your mouse. There are rollers inside the mouse that will pickup and accumulate dust & derbies. The ball itself will also pickup dust and eventually make your mouse feel as though it is full of gravel. Keeping your mouse pad clean is just as important so the mouse dosen't pick up too much dust. Mouse pads are usually made of noepreme rubber and can be washed in the sink with ordinary soap and then air dried. When cleaning out your mouse, make sure you get all the dust balls out of the cavity and that the rollers are completely clean. For optical mice, check to make sure the sender/pickup is free of dust.