var image_array = new Array[];

  // path to the directory with images
  var path = 'images/';

  // enumeration of the "active" images
image_array[0] = path + "leftpic_on.jpg";
image_array[1] = path + "rightpic_on.jpg";



var preload_image = new Array ();

  for(var i=0; i<image_array.length; i++)
  {
    preload_image[i]= new Image();
    preload_image[i].src = image_array[i];
  }

function rollover(name, filename)
{
  var fullpath = 'images/' + filename;
  document.images[name].src = fullpath;
}