function validateform()
{        
    var ok = true;
    var alertback = "";
 
    var naam = document.getElementById('naam').value;
    if(naam == "") {
        ok = false;   
        alertback = alertback + "Voornaam is verplicht \n";  
    }
    
    naam = document.getElementById('achternaam').value;
    if(naam == "") {
        ok = false;   
        alertback = alertback + "Achternaam is verplicht \n";  
    }
    
    naam = document.getElementById('adres').value;
    if(naam == "") {
        ok = false;   
        alertback = alertback + "Adres is verplicht \n";  
    }
    
    var filterzipcode = /^\d{4}[\s-]?[a-zA-Z]{2}$/;
    var zipcode = document.getElementById('postcode');
    if (!filterzipcode.test(zipcode.value)) {
        ok = false;
        alertback = alertback + "Postcode is verplicht (vb 1234AA) \n";
    }      
    
    naam = document.getElementById('plaats').value;
    if(naam == "") {
        ok = false;   
        alertback = alertback + "Plaats is verplicht \n";  
    }      
    
    var email = document.getElementById('mail');
    var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
    if (!filter.test(email.value)) {
        ok = false;   
        alertback = alertback + "E-mail is verplicht (vb myname@myproivder.nl) \n";   
    }
    
    var filtertelefoon = /^\d{3,4}( |-)?\d{6,7}$/;         
    var tel = document.getElementById('tel').value;
    if(!filtertelefoon.test(tel)) {
        ok = false;
        alertback = alertback + "Telefoonnummer is verplicht (vb 0612345678) \n"; 
    }
    
    naam = document.getElementById('leeftijd').value;
    if(isNaN(naam)) {
        ok = false;   
        alertback = alertback + "Leeftijd alleen getallen (vb 36) \n";  
    }
    
    if(!ok)
    {
        alert(alertback);
        return false;
    }
    
    AddParam('Naam', document.getElementById('naam').value+" "+document.getElementById('achternaam').value);
    AddParam('Adres', document.getElementById('adres').value);
    AddParam('Postcode', document.getElementById('postcode').value);
    AddParam('Plaats', document.getElementById('plaats').value);
    AddParam('E-Mail', document.getElementById('mail').value);
    AddParam('Telefoonnummer', document.getElementById('tel').value);
    AddParam('Leeftijd', document.getElementById('leeftijd').value);
    
    document.getElementById('formdiv').innerHTML = "Een ogenblik geduld...";
    
    postMethod('mail.php', getResult);
    return true;
}

function getResult(response) {
	if(http.readyState == 4 && http.status == 200) {
    document.getElementById('formdiv').innerHTML = http.responseText; 
  }
}