js操作cookie

穿转载自http://www.w3cschool.cc/js/js-cookies.html
//设置cookie,参数依次为，cookie键值，cookie值，cookie时间(代表天数)

        function setCookie(cname,cvalue,exdays){
            var d = new Date();
            d.setTime(d.getTime()+(exdays*24*60*60*1000));
            var expires = "expires="+d.toGMTString();
            document.cookie = cname + "=" + cvalue + "; " + expires;
        }
        //获取cookie
        function getCookie(cname){
            var name = cname + "=";
            var ca = document.cookie.split(';');
            for(var i=0; i<ca.length; i++)
              {
              var c = ca[i].trim();
                if (c.indexOf(name)==0) 
                    return c.substring(name.length,c.length);
              }
            return "zj";
        }
        //删除cookie
        function delCookie (cookie_name) {
            document.cookie = cookie_name+"=; expires=Thu, 01 Jan 1970 00:00:00 GMT";
        }

不知道为什么，今天在本地测，删除cookie是成功的，昨天在服务器上面，删除cookie死活不行，服务器系统也是windows啊。。。。。
昨天不成功解决办法

var date=new Date();
date.setTime(date.getTime()-10000);
document.cookie=cookie_name+"=zj; expire="+date.toGMTString()+"; path=/";