Dangerous dog

Upon entering the little country store, the stranger noticed a sign on the glass door "Danger! Beware of dog!". Inside he noticed a harmless old hound dog asleep on the floor beside the cash register. The stranger couldn't help but be amused. "That certainly doesn't look like a dangerous dog to me. Why in the world would you post that sign?" "Because," the owner replied, "before I posted that sign, people kept tripping over him."