var rotate_delay = 5000; <!-- delay 5000 ms = 5 secs -->
current = 0;

function next() 
 {
  if (document.slideform.slide[current+1]) 
  {
   document.images.show.src = document.slideform.slide[current+1].value;
   document.slideform.slide.selectedIndex = ++current;
  }
  else first();
 }

function previous() 
 {
  if (current-1 >= 0) 
  {
   document.images.show.src = document.slideform.slide[current-1].value;
   document.slideform.slide.selectedIndex = --current;
  }
  else last();
 }

function first() 
 {
  current = 0;
  document.images.show.src = document.slideform.slide[0].value;
  document.slideform.slide.selectedIndex = 0;
 }

function last() 
 {
  current = document.slideform.slide.length-1;
  document.images.show.src = document.slideform.slide[current].value;
  document.slideform.slide.selectedIndex = current;
 }

function ap(text) 
 {
  document.slideform.slidebutton.value = (text == "Stop") ? "Play" : "Stop";
  rotate();
 }

function change() 
 {
  current = document.slideform.slide.selectedIndex;
  document.images.show.src = document.slideform.slide[current].value;
 }

function rotate() 
 {
  if (document.slideform.slidebutton.value == "Stop") 
  {
   current = (current == document.slideform.slide.length-1) ? 0 : current+1;
   document.images.show.src = document.slideform.slide[current].value;
   document.slideform.slide.selectedIndex = current;
   window.setTimeout("rotate()", rotate_delay);
  }
 }

<!-- taken from: http://www.ricocheting.com -->