function randomBannerPic() {
  /*The path to the folder containing the banner images*/
  var images_path = '/images/heads/';
  
  var pic_array = new Array();
  /*populate the array with the banner images*/
  pic_array[0] = 'head1.jpg';
  pic_array[1] = 'head3.jpg';
  pic_array[2] = 'head4.jpg';
  pic_array[3] = 'head6.jpg';
  pic_array[4] = 'head7.jpg';
  pic_array[5] = 'head8.jpg';

  /*randomly choose a banner image to display*/
  var display_pic_index = Math.floor(Math.random()*(pic_array.length-0.01));
  
  /*assemble the url for the banner image*/
  var display_pic_url = images_path + pic_array[display_pic_index];
  
  /*change the banner image to the randomly selected banner picture*/
  document.banner_face.src = display_pic_url;
}