Digital Photography Tip One – Busting The Dust:
Digital SLRs with removable lenses are prone to dust landing on the sensor. Static electricity around the sensor can possibly contribute to attracting dust particles, or other elements to this sensitive area of your camera.
To get rid of the dust you can use a camera blower brush, and tilt the camera down while blowing. Take care not to get any of the hairs snagged inside!