title: onFocus and onBlur attribute in zk?
body: <p>Before I google :</p>
  
  <p><a href="http://www.zkoss.org/zkdemo/event/client-side_event_handling" rel="nofollow">http://www.zkoss.org/zkdemo/event/client-side_event_handling</a></p>
  
  <p>But i dont undetstand clearly .</p>
  
  <p>pls tell me:</p>
  
  <p>What is the purpose of use onFocus and onBlur attribute in zk ?</p>