如何使用倒计时jquery插件

我在互联网上使用源代码。它只显示正确，但没有结果。这里是我的代码如何使用倒计时jquery插件

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
    <html xmlns="http://www.w3.org/1999/xhtml"> 
     <head> 
      <link rel="stylesheet" type="text/css" href="style.css" /> 
      <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js" type="text/javascript"></script> 
      <script src="jquery.countdown.packed.js" type="text/javascript"></script> 
      <script type="text/javascript"> 
       $(function() { 
        $('#countdown').countdown({until:$.countdown.UTCDate(-8, 2011, 1 - 1, 1), format: 'DHMS', layout: 
         '<div id="timer">' + '<hr />'+ 
          '<div id="timer_days" class="timer_numbers">{dnn}</div>'+ 
          '<div id="timer_hours" class="timer_numbers">{hnn}</div>'+ 
          '<div id="timer_mins" class="timer_numbers">{mnn}</div>'+ 
          '<div id="timer_seconds" class="timer_numbers">{snn}</div>'+ 
          '<div id="timer_labels">'+ 
           '<div id="timer_days_label" class="timer_labels">days</div>'+ 
           '<div id="timer_hours_label" class="timer_labels">hours</div>'+ 
           '<div id="timer_mins_label" class="timer_labels">mins</div>'+ 
           '<div id="timer_seconds_label" class="timer_labels">secs</div>'+ 
          '</div>'+       
         '</div>'      
        }); 
       }); 
      </script> 
     <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> 
     <title>Untitled Document</title> 
    </head> 
    <body> 
     <div id="countdown"></div> 
    </body> 
</html>

这是导致

enter image description here