div{margin:30px;
width:200px;
height:200px;
  line-height:200px;
  text-align:center;
background-color:#ff6a2f;
  -webkit-transition: 0.3s ease;
    -moz-transition: 0.3s ease;
    -ms-transition: 0.3s ease;
    -o-transition: 0.3s ease;
    transition: 0.3s ease;
}
div.on{/* Rotate div */
transform:rotate(90deg);
-ms-transform:rotate(90deg); /* Internet Explorer */
-moz-transform:rotate(90deg); /* Firefox */
-webkit-transform:rotate(90deg); /* Safari 和 Chrome */
-o-transform:rotate(90deg); /* Opera */}