function readCookie(name) {
                    var nameEQ = name + "=";
                    var ca = document.cookie.split(';');
                    for(var i=0;i < ca.length;i++) {
                        var c = ca[i];
                        while (c.charAt(0)==' ') c = c.substring(1,c.length);
                        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
                    }
                    return null;
                }