// Conta caracteres
function ContaCaracteres(){
   intCaracteres = 355 - document.form.cp_msg.value.length;
   if (intCaracteres > 0){
      document.form.caracteres.value = intCaracteres;
      return true;
   }
   else {
      document.form.caracteres.value = 0;
      document.form.cp_msg.value = document.form.cp_msg.value.substr(0,255)
      return false;
   }
}