//客户端操作cookie
            //获取cookie
            function getCookie(cookieName)
            {
                var cookieString = document.cookie;
                var start = cookieString.indexOf(cookieName + '=');
                //加上等号的原因是避免在某些Cookie的值里有
                //与cookieName一样的字符串。
                if (start == -1)//找不到
                    return null;
                start += cookieName.length + 1;
                var end = cookieString.indexOf(';', start);
                if (end == -1) 
                    return unescape(cookieString.substring(start));
                return unescape(cookieString.substring(start, end));
            }
            //设置cookie
            function setCookie(cookieName, value)
            {
                var expires = new Date();
                expires.setTime(expires.getTime() + 3*30*24*60*60*1000);
                //if (getCookie(cookieName)==null)
                    document.cookie = cookieName + '=' + escape(value) + ';' + 'expires=' + expires.toGMTString();
                //else
                //    document.cookie = cookieName + "=" + escape(value) + ";" + "expires=' + expires.toGMTString();
            }