var intervalID;
var start_frame = 0;
var end_frame = 2;
var frame = 0;
var interval = 3;  
  
function startSlide()   
{   
  intervalID = setInterval(contentSlide, (interval*1000));   
}   
  
function contentSlide()   
{
 for (var i = start_frame; i <= end_frame; i++){ 
  var Layer_Name = 'slideshow' + i;  
  var elem = document.getElementById(Layer_Name);
  elem.style.display = 'none';      
  }
  if (frame == end_frame) {frame = start_frame;} else {frame = frame + 1;}
  var Layer_Name = 'slideshow' + frame;
  var elem = document.getElementById(Layer_Name);
  //alert(Layer_Name + " = " + elem.style.display);   
  elem.style.display = 'block';       
}

function stopSlide()   
{   
  clearInterval(intervalID);   
}