function checkSbox(aj){
    var keyword = document.main_search.keyword.value;
    if ((keyword.length < 3) || (keyword.length > 15)){
        mesg = "Tu khoa khong du dai. Xin dien lai"
        alert(mesg);

        document.main_search.keyword.focus();
        return (false);
    }
    if(aj){
    	ajaxpage("mylink?func=search&keyword="+keyword,"s756356");
        return (false);
    }else
        return (true);
}