Dojo kun is a Japanese martial arts term literally meaning (training hall) rules. They are generally posted at the entrance to dojo or at the "front" of the dojo (shomen) and outline behaviour expected and disallowed. In some styles of martial arts they are recited at the end of a class.
Read more about Dojo Kun: Shotokan Karate, Goju Ryu, Ryu-te, Bushido, Budōkan, Derivation