if (document.images) {
  
  image6on = new Image();
  image6on.src = "images/nl_on.gif";

  image6off = new Image();
  image6off.src = "images/nl_off.gif"; 
      
  image16on = new Image();
  image16on.src = "images/fra_on.gif";
  
  image16off = new Image();
  image16off.src = "images/fra_off.gif";
  
}


function changeImages() {
  if (document.images) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
    }
  }
}