JAVASCRIPT

jquery fade opacity

<div id="clickme">
  Click here
</div>
<img id="book" src="book.png" alt="" width="100" height="123">
// With the element initially shown, we can dim it slowly:
$( "#clickme" ).click(function() {
  $( "#book" ).fadeTo( "slow" , 0.5, function() {
    // Animation complete.
  });
});