.crossfade {
  position:relative;
  max-width:100%;
  margin:0 auto;
}

.crossfade img {
  position:absolute;
  max-width:100%;
  left:0;
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  transition: opacity 1s ease-in-out;
}

.crossfade img.top:hover {
  opacity:0;
}