if (document.images)
   {
     pic1on= new Image(49,43);
     pic1on.src="img/cast_01.jpg";
     pic2on= new Image(63,43);
     pic2on.src="img/cast_02.jpg";
     pic3on= new Image(83,43);
     pic3on.src="img/cast_03.jpg";

     pic1off= new Image(49,43);
     pic1off.src="img/cast_01.png";
     pic2off= new Image(63,43);
     pic2off.src="img/cast_02.png";
     pic3off= new Image(83,43);
     pic3off.src="img/cast_03.png";
   }

function lightup(imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + "on.src");
      document[imgName].src= imgOn;
    }
 }

function turnoff(imgName)
 {
   if (document.images)
    {
      imgOff=eval(imgName + "off.src");
      document[imgName].src= imgOff;
    }
 }