FoulsCode.blogspot.gr

<style>
img {
  position: absolute;
  left: 10px;
  top: 60px;
  display: block;
  clip: rect(200px, 0, 0, 400px);
  -webkit-transition: all 0.5s ease-out;
  -moz-transition: all 0.5s ease-out;
  transition: all 0.5s ease-out;
}

span:hover ~ img {
  clip: rect(0, 400px, 200px, 0);
}

span {
  display: inline-block;
  padding: 10px;
  margin: 10px;
  background: #08C;
  color: white;
  font-family: "Helvetica", "Arial", sans-serif;
  font-weight: bold;
  text-shadow: 0 -1px rgba(0,0,0,0.3);
  text-align: center;
  cursor: pointer;
}

span:hover {
  background: #09C;
}
</style>
<span>Hover me</span>
<img src="http://lorempixel.com/400/200/">