function ImageSwapSetup()
{
  var images = document.getElementsByTagName("img");
  
  for (var i=0;i<images.length;i++)
  {
    images[i].oversrcimg = new Image();
    images[i].oversrcimg.src = images[i].getAttribute("src").replace("off.", "on.");

    images[i].onmouseover = new Function("ImageSwap(this, 'oversrc');");
    images[i].onmouseout = new Function("ImageSwap(this);");

    images[i].setAttribute("origsrc", images[i].src);
    images[i].setAttribute("oversrc", images[i].oversrcimg.src);
  }
}

function ImageSwap(el,which)
{
  el.src=el.getAttribute(which||"origsrc");
}
  
window.onload = function() { ImageSwapSetup(); }