if(document.images)
{
  var image_array = new Array();
	
  // path to the directory with images
  var path = "images/";

  // enumeration of the "active" images
  image_array[0] = path + "b_1_over.jpg";
  image_array[1] = path + "b_2_over.jpg";
  image_array[2] = path + "b_3_over.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;
}