There was an old man and an old woman sitting on the porch in their rocking 
chairs not saying a word to each other.  All of a sudden the old lady reached 
over and punched the old man as hard as she could and the old man fell out of 
his rocker.  After getting ahold of himself, he got back in his rocker and 
asked "What was that for?"

The old lady replied "That was for 40 years of bad sex."

They sat there for a little while and the little old man reached across and 
backhanded the old gal right out of her chair.  After brushing herself off, 
she asked "And what was that for?"

He stated, "For knowing the difference!"