function validate(){
                var df=document.forms['login'];
                if(df['login_name'].value==''){
                        alert('Please enter login name.');
                        df['login_name'].focus();
                        return(false);
                }
                if(df['password'].value==''){
                        alert('Please enter password.');
                        df['password'].focus();
                        return(false);
                }
                return(true);
        }