Ajax Progress update end request

script type="text/javascript"

   var prm = Sys.WebForms.PageRequestManager.getInstance();
   prm.add_initializeRequest(InitializeRequest);
   prm.add_endRequest(EndRequest);
   var postBackElement;
   function InitializeRequest(sender, args) {
      if (prm.get_isInAsyncPostBack())
      {
         args.set_cancel(true);
      }
      postBackElement = args.get_postBackElement();
      if (postBackElement.id == 'ButtonTrigger')
      {
        $get('UpdateProgress1').style.display = "block";
      }
   }
   function EndRequest (sender, args) {
      if (postBackElement.id == 'ButtonTrigger')
      {
        $get('UpdateProgress1').style.display = "none";   
      }
   }
   function AbortPostBack() {
     if (prm.get_isInAsyncPostBack()) {
          prm.abortPostBack();
     }       
   }
/ script

http://www.asp.net/ajax/documentation/live/ViewSample.aspx?sref=UpdateProgressOverview2