Beware of dog
Upon entering the little country store, the stranger noticed a sign saying "DANGER! BEWARE OF DOG!" posted on the glass door. Inside he noticed a harmless old hound dog asleep on the floor besides the cash register.
He asked the store manager, "Is THAT the dog folks are supposed to beware of?"
"Yep, that's him," he replied.
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."