Before bringing a new dog home, know its history and breed. Certain pedigrees are very aggressive. Bites usually occur from a dog familiar to the child or his family. Don't leave young children alone with a dog. All dogs are different, and some are more prone to violent behavior.
All dogs are potentially dangerous.
Even the friendliest dogs can bite. Don't run when approached by a threatening dog. Instead, be quiet, and stand very still. If the child gets knocked down, he should lie facedown with his legs together, fists behind his neck and ears covered with his forearms. Never disturb a sleeping dog.