Jquery:Disable right click without alert

Demo

 <a class="demo" href="http://jithuan.blogspot.com/">Demo</a>   
  <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>   
  <script type="text/javascript">   
    $(document).ready(function(){   
       $(".demo").mousedown(function(event) {   
         $(this).attr('oncontextmenu',"return false");   
       });   
    });   
  </script>