There can be several reasons for your dog scooting his bottom across the floor. Dogs have sacs just inside the anus called anal glands, sometimes these glands can become full or infected, the scooting is the dogs way of trying to empty the glands. Other reasons could be diarrhea, or an allergy. Very rarely the scooting could be caused by intestinal parasites, specifically tapeworms. If you notice your dog scooting or licking his bottom more than usual the best thing to do is have it checked by your veterinarian. Your veteriarian can find the cause of the scooting and help make your dog feel better.