if (document.images)
   {
     pic1on= new Image;
     pic1on.src="../img/button1a.jpg";  
     pic2on= new Image;
     pic2on.src="../img/button2a.jpg"; 
     pic3on= new Image;
     pic3on.src="../img/button3a.jpg"; 
     pic4on= new Image;
     pic4on.src="../img/button4a.jpg";
     pic5on= new Image;
     pic5on.src="../img/button5a.jpg";
     pic6on= new Image;
     pic6on.src="../img/button6a.jpg";
     pic1off= new Image;
     pic1off.src="../img/button1.jpg";
     pic2off= new Image;
     pic2off.src="../img/button2.jpg";
     pic3off= new Image;
     pic3off.src="img/button3.jpg";
     pic4off= new Image;
     pic4off.src="../img/button4.jpg";
     pic5off= new Image;
     pic5off.src="../img/button5.jpg";
     pic6off= new Image;
     pic6off.src="../img/button6.jpg";
   }
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;
    }
 }