Simple Slideshow

<style>
/* the slide container with a fixed size */
.slides {
  box-shadow: 0px 0px 6px black;
  margin: 0 auto;
  width: 500px;
  height: 300px;
  position: relative;
}

/* the images are positioned absolutely to stack. opacity transitions are animated. */
.slides img {
  display: block;
  position: absolute;
  transition: opacity 1s;
  opacity: 0;
  width: 100%;
}

/* the first image is the current slide. it's faded in. */
.slides img:first-child {
  z-index: 2; /* frontmost */
  opacity: 1;
}

/* the last image is the previous slide. it's behind the current slide and it's faded over. */
.slides img:last-child {
  z-index: 1; /* behind current slide */
  opacity: 1;
}
</style>

<div class="slides">
  <img src="http://lorempixel.com/500/300/?r=1">
  <img src="http://lorempixel.com/500/300/?r=2">
  <img src="http://lorempixel.com/500/300/?r=3">
  <img src="http://lorempixel.com/500/300/?r=4">
  <img src="http://lorempixel.com/500/300/?r=5">
</div>

<script>
function nextSlide() {
    var q = function(sel) { return document.querySelector(sel); }
    q(".slides").appendChild(q(".slides img:first-child"));
}
setInterval(nextSlide, 3000)
</script>