function ValidateForm(form)
{
   if(IsEmpty(form.naam)) 
   { 
      alert('You have not entered an account number') 
      form.naam.focus(); 
      return false; 
   } 
 
 
   if (!IsNumeric(form.adres.value)) 
   { 
      alert('Please enter only numbers or decimal points in the account field') 
      form.adres.focus(); 
      return false; 
      } 
 
return true;
 
} 

    function ajaxRequest(button, status)
    {
        if(window.XMLHttpRequest)
        {
            var request = new XMLHttpRequest ();
        }
        else
        {
            var request = new ActiveXObject ("Microsoft.XMLHTTP");
        }
         
        request.onreadystatechange = function ()
        {
            button.disabled = true;
            document.getElementById(status).innerHTML = "Even geduld aub.";

            if(request.readyState == 4)
            {
                if(request.status == 200)
                {
                    eval('response(request.responseText)');
                    document.getElementById("naam").value = "";
                    document.getElementById("adres").value = "";
                    document.getElementById("postcode").value = "";
                    document.getElementById("telefoonnummer").value = "";
                }
                else
                {
                    button.disabled = false;
                    document.getElementById(status).innerHTML = "Error. Probeer het opnieuw.";
                }
            }
        }
    
        request.open("POST", "check.php", true);
        request.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
        
        var naam = 'n=' + encodeURI(document.getElementById("naam").value);
        var email = '&e=' + encodeURI(document.getElementById("adres").value);
        var onderwerp = '&o=' + encodeURI(document.getElementById("postcode").value);
        var bericht = '&b=' + encodeURI(document.getElementById("telefoonnummer").value);
        
        request.send(naam + adres + postcode + telefoonnummer);
        
        return false;
    }
    
    function response(result)
    {
        result_code = result.split("::");

        if(result_code[0] == "error")
        {
            document.getElementById('status').innerHTML = result_code[1];
        }
    }