A council in Britain has banned its staff from cracking mother-in-law jokes. Such humor is no longer acceptable, according to officials at the London Borough of Barnet. Daily Telegraph reported Monday that the order was issued in a 12-page booklet called "Cultural awareness: General Problems". "Humor can be incredibly culture-specific, and is very open to misinterpretation or even offense by other cultures. And don't forget when you don't know what people are laughing at, it is very easy to imagine that they are laughing at you.