"See no evil, talk no evil, hear no evil" is an idiom from a Japanese pictorial saying depicting three wise monkeys. The three monkeys are Mizaru, covering his eyes, who sees no evil; Kikazaru, covering his ears, who hears no evil; and Iwazaru, covering his mouth, who speaks no evil. There are various meanings ascribed to the phrase and the proverb including associations with being of good mind, speech and action. In Buddhist tradition, the tenets of the proverb are about not dwelling on evil thoughts. In the Western world both the proverb and the image are often used to refer to a lack of moral responsibility on the part of people who refuse to acknowledge impropriety, looking the other way or feigning ignorance.

It's an old Japanese proverb that has been translated into English. It refers to the legend of the Three Wise Monkeys that can't see, hear or speak evil. There's speculation that the concept was introduced to Japan from China centuries earlier. You can read about the monkeys here: http://luxeyard.wordpress.com/2012/07/23/the-legend-of-the-three-wise-monkeys/

it means "do no evil"

A joke version I have seen has a fourth monkey - with his hands over his privates - and 'do no evil'...