title: Password filled blank after postback
body: <p>When I set the <code>textmode = Password</code> the value of the textbox is lost after the postback since 
  as I know the textbox class implement the interface <code>IpostbcakdataHandler</code> so that it retains the value either we disable the textbox viewstate false.</p>
  
  <p>So I want to know the reason why it is happening.</p>