if (document.images)
   {

     pic1on= new Image(200,35);
     pic1on.src="pic/g1k.png";  
     pic1off= new Image(200,35);
     pic1off.src="pic/g1.png";

     pic2on= new Image(200,35);
     pic2on.src="pic/g2k.png";  
     pic2off= new Image(200,35);
     pic2off.src="pic/g2.png";

     pic3on= new Image(200,35);
     pic3on.src="pic/g3k.png";  
     pic3off= new Image(200,35);
     pic3off.src="pic/g3.png";

     pic4on= new Image(200,35);
     pic4on.src="pic/g4k.png";  
     pic4off= new Image(200,35);
     pic4off.src="pic/g4.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;
    }
 }