var rotate_delay = 2500; // delay in milliseconds (5000 = 5 secs)
current = -1;

var img_array = new Array(18);

img_array[0] = 'thumbnails_nils/1.png';
img_array[1] = 'thumbnails_nils/2.png';
img_array[2] = 'thumbnails_nils/3.png';
img_array[3] = 'thumbnails_nils/4.png';
img_array[4] = 'thumbnails_nils/5.png';
img_array[5] = 'thumbnails_nils/6.png';
img_array[6] = 'thumbnails_nils/7.png';
img_array[7] = 'thumbnails_nils/8.png';
img_array[8] = 'thumbnails_nils/9.png';
img_array[9] = 'thumbnails_nils/10.png';
img_array[10] = 'thumbnails_nils/11.png';
img_array[11] = 'thumbnails_nils/12.png';
img_array[12] = 'thumbnails_nils/13.png';
img_array[13] = 'thumbnails_nils/14.png';
img_array[14] = 'thumbnails_nils/15.png';
img_array[15] = 'thumbnails_nils/16.png';
img_array[16] = 'thumbnails_nils/17.png';
img_array[17] = 'thumbnails_nils/18.png';
img_array[18] = 'thumbnails_nils/19.png';
img_array[19] = 'thumbnails_nils/20.png';


function rotate() {
  current = (current >= img_array.length-1) ? 0 : current+1;
  document.images.show.src = img_array[current];
  window.setTimeout("rotate()", rotate_delay);
}