function changeTab(tab) {
        switch (tab) {
            case 'en':
                document.getElementById('tab_en').style.display = 'block';
                document.getElementById('tab_cz').style.display = 'none';
                document.getElementById('tab_de').style.display = 'none';
                
                document.getElementById('link_en').style.color = '#ff0000';
                document.getElementById('link_cz').style.color = '#0000ff';
                document.getElementById('link_de').style.color = '#0000ff';
                
                if (document.form_mutate) {
                    document.form_mutate.form_send_language.value = 'en';
                }
                break;
            case 'cz':
                document.getElementById('tab_en').style.display = 'none';
                document.getElementById('tab_cz').style.display = 'block';
                document.getElementById('tab_de').style.display = 'none';

                document.getElementById('link_en').style.color = '#0000ff';
                document.getElementById('link_cz').style.color = '#ff0000';
                document.getElementById('link_de').style.color = '#0000ff';

                if (document.form_mutate) {
                    document.form_mutate.form_send_language.value = 'cz';
                }
                break;
            case 'de':
                document.getElementById('tab_en').style.display = 'none';
                document.getElementById('tab_cz').style.display = 'none';
                document.getElementById('tab_de').style.display = 'block';

                document.getElementById('link_en').style.color = '#0000ff';
                document.getElementById('link_cz').style.color = '#0000ff';
                document.getElementById('link_de').style.color = '#ff0000';

                if (document.form_mutate) {
                    document.form_mutate.form_send_language.value = 'de';
                }
                break;
            default:
                return false;
                break;
        }
        return true;
    }
    
    function checkForm() {
        if (document.getElementById('demandForm').form_phone.value == '') {
            window.alert('Zadejte telefon!');
            document.getElementById('demandForm').form_phone.focus();
            return false;
        }
        if (document.getElementById('demandForm').form_email.value == '') {
            window.alert('Zadejte e-mail!');
            document.getElementById('demandForm').form_email.focus();
            return false;
        }
        if (document.getElementById('demandForm').form_protect.value == '') {
            window.alert('Zadejte odpoved!');
            document.getElementById('demandForm').form_protect.focus();
            return false;
        }
        return true;
    }
    
//    function checkForm(arr) {
//        for (var i = 0; i < arr.length; i++) {
//            switch (arr[i]) {
//                case 'name':
//                    if (document.getElementById('editForm').form_name.value == '') {
//                        alert('jmeno!');
//                        document.getElementById('editForm').form_name.focus();
//                        return false;
//                    }
//                    break;
//            }
//        }
//        return false;
//    
//    }