function switchImage(imgName, imgSrc) 
{
  if (document.images)
  {
    if (imgSrc != "none")
    {
      document.images[imgName].src = imgSrc;
    }
  }
}

fPreload( 'home_mo.gif','donate_mo.gif','recipe_mo.gif','contact_mo.gif'); 
function fPreload()
{ 
  var args = fPreload.arguments;
  document.imageArray = new Array(args.length);
  for(var i=0; i<args.length; i++)
  {
    document.imageArray[i] = new Image;
    document.imageArray[i].src = '../images/'+args[i];
  }
}