<!--
  if (document.images)
   {           
  img1on = new Image();
  img1on.src = "index/a1.gif";
  img2on = new Image();
  img2on.src = "index/b1.gif";
  img1off = new Image();
  img1off.src = "index/a.gif";
  img2off = new Image();
  img2off.src = "index/b.gif";
    }
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");
     }
  }
// -->