$(function () {

 

 /***每隔5分钟改变一次验证码 jquery 扩展方法 ***/          

   $.extend({              

   referesh1: function () {              

       myDate = new Date();                    

 $("#<%=Image1.ClientID %>").attr("src", "../DisplayCheckNum.aspx?guid=" + myDate.getTime());         

        }       

      });

            timerID = setInterval("$.referesh1()", 1000 * 60 * 5);

 

  });