if (document.images) {
  m01a = new Image();
  m01a.src = "img/m1_a.gif";
  m01n = new Image();
  m01n.src = "img/m1_n.gif";
  m02a = new Image();
  m02a.src = "img/m2_a.gif";
  m02n = new Image();
  m02n.src = "img/m2_n.gif";
  m03a = new Image();
  m03a.src = "img/m3_a.gif";
  m03n = new Image();
  m03n.src = "img/m3_n.gif";
  m04a = new Image();
  m04a.src = "img/m4_a.gif";
  m04n = new Image();
  m04n.src = "img/m4_n.gif";
}