function check_email(email) {
    invalid = " /:,;";
    if(email == "") { return false }
    for(i=0; i < invalid.length; i++) {
        bad = invalid.charAt(i);
        if (email.indexOf (bad, 0) != -1) { return false }
    }
    at = email.indexOf("@", 0);
    if( (at == -1) || (at == 0) ) { return false }
    if(email.indexOf("@", at+1) != -1) { return false }
    period = email.indexOf(".", at);
    if( (period == -1) || (period == at+1) ) { return false }
    if(period+3 > email.length == -1) { return false }
    return true;
}

function zapisz(form) {
    if (!(check_email(form.email.value))) {
        alert('Podaj poprawny adres e-mail.');
        form.email.focus();
        form.email.select();
        return false;
    }
    else {
        return true;
    }
}