function tours_subscribe_is_disabled() {

    var frm = document.forms[0];

    b_disabled = true;

    if ( frm.email.value.match(/[^\s]/) ) {

        // Looking for one checked checkbox
        cbs = frm['entids[]'];

        for ( i=0; i<cbs.length; i++ ) {
            if ( cbs[i].checked ) {
                b_disabled = false;
                break;
            }
        }

    }

    return b_disabled;
}

function tours_subscribe_load() {

    var frm = document.forms[0];

    // Updating checkboxes if checkbox "All" is checked
    tour_subscribe_all_click(frm.entids_0);

    // Deactivating submit button
    frm.bt_submit.disabled=tours_subscribe_is_disabled();
}

function tour_subscribe_all_click(sender) {

    cbs = document.forms[0]['entids[]'];

    var value = sender.checked;

    for ( i=0; i<cbs.length; i++ ) {

        if ( cbs[i].id != 'entids_0' ) {
            cbs[i].disabled = value;
        }
    }

    // Deactivating submit button
    document.forms[0].bt_submit.disabled=tours_subscribe_is_disabled();

}


function tour_subscribe_change(sender) {

    // Deactivating submit button
    document.forms[0].bt_submit.disabled=tours_subscribe_is_disabled();

}

function tour_subscribe_check( frm ) {

    if ( !frm.email.value.match(/^[a-z0-9_\-\.]+@([a-z0-9_\-]+\.)+[a-z]{2,5}$/i) ) {
        alert("Неправильный ввод в поле E-mail");
        frm.email.focus();
        frm.email.select();
        return false;
    }

    b_checked = false;
    i_len     = frm["entids[]"].length;
    for (i=0; i<i_len; i++) {
        if ( frm["entids[]"][i].checked ) {
            b_checked = true;
            break;
        }
    }

    if ( !b_checked ) {
        alert("Вы не выбрали ни одного вида отдыха");
        return false;
    }

    return true;
}