function valid(lang)
{
    var valid = true;
    var fields    = new Array("naam","adres","postcode","plaats","vraag_opmerking");
    var fields_nl = new Array("Naam","Adres","Postcode","Plaats","Vraag/Opmerking");
    var fields_en = new Array("Name","Adress","Postcode","Place","Question/Comment");
    for(var i=0; i<fields.length; i++)
    {
        if(eval("document.frm."+fields[i]).value=="")
        {
            if(lang=="nl")
            {
                alert("Het veld \""+fields_nl[i]+"\" is verplicht.");
            }
            else
            {
                alert("The field \""+fields_en[i]+"\" is required.");
            }
            valid = false;
            eval("document.frm."+fields[i]).focus();
            break;
        }
    }

    if(valid)
    {
        document.frm.method = "POST";
        document.frm.action = "/custom/sendContact.php";
        document.frm.submit();
    }
}