Fond du Lac, Wis. (WHBL) - A fatal accident in Fond du Lac County this morning.  The Sheriff’s Department said 27 year old William Pfeiffer of Rosendale was driving a car that crossed the centerline on Highway 23 and collided with a semi.  The semi rolled over on impact.  Pfeiffer was partially ejected but pinned in his car.  He died a short time later at Theda Clark Regional Medical Center in Neenah.  The driver of the semi was not injured. The mishap occurred about 5 this morning and disrupted traffic on Highway 23 for nearly 3 hours.