r1on = new Image;
  r1of = new Image;
  r2on = new Image;
  r2ona = new Image;
  r2of = new Image;
  r3on = new Image;
  r3of = new Image;
  r4on = new Image;
  r4ona = new Image;
  r4of = new Image;
  r5on = new Image;
  r5of = new Image;
  r6on = new Image;
  r6ona = new Image;
  r6of = new Image;
  r7on = new Image;
  r7of = new Image;
  r8on = new Image;
  r8ona = new Image;
  r8of = new Image;
  r9on = new Image;
  r9of = new Image;
  
  r1on.src = "img/nav-1a-on.gif";
  r1of.src = "img/nav-1a-off.gif";  
  r2on.src = "img/nav-1b-on.gif";
  r2ona.src = "img/nav-1b-ona.gif";
  r2of.src = "img/nav-1b-off.gif";
  r3on.src = "img/nav-2a-on.gif";
  r3of.src = "img/nav-2a-off.gif";
  r4on.src = "img/nav-2b-on.gif";
  r4ona.src = "img/nav-2b-ona.gif";
  r4of.src = "img/nav-2b-off.gif";
  r5on.src = "img/nav-3a-on.gif";
  r5of.src = "img/nav-3a-off.gif";
  r6on.src = "img/nav-3b-on.gif";
  r6ona.src = "img/nav-3b-ona.gif";
  r6of.src = "img/nav-3b-off.gif";
  r7on.src = "img/nav-4a-on.gif";
  r7of.src = "img/nav-4a-off.gif";
  r8on.src = "img/nav-4b-on.gif";
  r8ona.src = "img/nav-4b-ona.gif";
  r8of.src = "img/nav-4b-off.gif";
  r9on.src = "img/nav-5a-on.gif";
  r9of.src = "img/nav-5a-off.gif";