if (document.images) {
   img1on = new Image()
   img1on.src="images/2a.jpg";
   
   img2on = new Image()
   img2on.src="images/3a.jpg";
   
   img3on = new Image()
   img3on.src="images/4a.jpg";
   
   img4on = new Image()
   img4on.src="images/5a.jpg";
   
   img5on = new Image()
   img5on.src="images/1a.jpg";

   img6on = new Image()
   img6on.src="images/6a.jpg";

  
   img1off = new Image()
   img1off.src="images/2.jpg"; 
   
   img2off = new Image()
   img2off.src="images/3.jpg"; 
   
   img3off = new Image()
   img3off.src="images/4.jpg"; 
   
   img4off = new Image()
   img4off.src="images/5.jpg"; 
   
   img5off = new Image()
   img5off.src="images/1.jpg"; 

   img6off = new Image()
   img6off.src="images/6.jpg"; 
     }
   
 function imgon(imgname) {
   if (document.images) {
       document[imgname].src=eval(imgname + "on.src");
       }
 }
 function imgoff(imgname) {
   if (document.images) {
       document[imgname].src=eval(imgname + "off.src");
       }
 }