var slideshow = new Array(3);
slideshow[0] = new Image();
slideshow[0].src = "http://koti.mbnet.fi/milones/lib/jpg.php?id=welcome";
slideshow[1] = new Image();
slideshow[1].src = "http://koti.mbnet.fi/milones/lib/jpg.php?id=welcome2";
slideshow[2] = new Image();
slideshow[2].src="http://koti.mbnet.fi/milones/lib/jpg.php?id=welcome3";

var timer;

function showImage(index) {
  if (document.images["welcome_image"]) {
    document.images["welcome_image"].src = slideshow[index].src;
    index++;
    if (index > 2) {
      index = 0;
    }

    timer = setTimeout(function() { showImage(index) }, 5000);
  }
  else {
    clearTimeout(timer);
  }
}