title: Stop disappearing ModalPopup panel (shown by ModalPopupExtender ) on changing text of a textbox (TextChanged event fired by AutoPostback)
body: <p>I have a html table inside of a panel control.
  It will be shown by a ModalPopupExtender by clicking on a LinkButton.</p>
  
  <p>inside of the panel, there is a textbox which its "AutoPostBack" property is Ture and when user enters a value in it, TextChanged event is fired but unfortunately, the panel also disapears.....</p>
  
  <p>what's wrong?</p>