$.extend($.ui.dialog.overlay, { create: function(dialog){  
  if (this.instances.length === 0) {  
    setTimeout(function() {  
      if ($.ui.dialog.overlay.instances.length) {  
        $(document).bind($.ui.dialog.overlay.events, function(event) {  
          var parentDialog = $(event.target).parents('.ui-dialog');  
          if (parentDialog.length > 0) {  
            var parentDialogZIndex = parentDialog.css('zIndex') || 0;  
            return parentDialogZIndex > $.ui.dialog.overlay.maxZ;  
          }  
          var aboveOverlay = false;  
          $(event.target).parents().each(function() {  
            var currentZ = $(this).css('zIndex') || 0;  
            if (currentZ > $.ui.dialog.overlay.maxZ) {  
              aboveOverlay = true;  
              return;  
            }  
          });  
          return aboveOverlay;  
        });  
      }  
    }, 1);  
    $(document).bind('keydown.dialog-overlay', function(event) {  
      (dialog.options.closeOnEscape && event.keyCode && event.keyCode == $.ui.keyCode.ESCAPE && dialog.close(event));  
    });  
    $(window).bind('resize.dialog-overlay', $.ui.dialog.overlay.resize);  
  }  
  var $el = $('<div></div> ').appendTo(document.body).addClass('ui-widget-overlay').css({  
 
    width: this.width(),  
    height: this.height()  
  });  
  (dialog.options.stackfix && $.fn.stackfix && $el.stackfix());  
  this.instances.push($el);  
  return $el;  
}});