function checkForm(form)
{
  var i;
  var leftpane = document.getElementById('leftPane');
  
  var prevErr = document.getElementById('formerror');
  if(prevErr)
    leftpane.removeChild(prevErr);

  var ideal = form.betalen[1].checked;
  
  var error = new Array();
  var c = 0;
  // Always required fields
  if(form.roepnaam.value.length == 0)
	  error[c++] = "roepnaam";
	if(form.voorletters.value.length == 0)
	  error[c++] = "voorletters";
	if(form.achternaam.value.length == 0)
	  error[c++] = "achternaam";
	if(form.telefoon.value.length != 10 && (form.mobiel.value.length != 10 || form.mobiel.value.substr(0, 2) != "06"))
	  error[c++] = "vast of mobiel telefoonnummer";
	// Only for contact
  if(!ideal && form.email.value.length == 0)
	  error[c++] = "e-mail adres";
  // Only for iDeal
  if(ideal) {
    if(!form.aanhef[0].checked && !form.aanhef[1].checked)
      error[c++] = "aanhef";
    if(form.straat.value.length == 0)
      error[c++] = "straatnaam";
    if(form.huisnr.value.length == 0 || Number(form.huisnr.value) != form.huisnr.value)
      error[c++] = "huisnummer";
    if(form.postcode.value.length != 6 && form.postcode.value.length != 7)
      error[c++] = "postcode";
    if(form.plaats.value.length == 0)
      error[c++] = "woonplaats";
    if(form.gebdag.selectedIndex == 0 || form.gebmaand.selectedIndex == 0)
      error[c++] = "geboorte datum";
  }

  if(c) {
    var div = document.createElement('div');
    div.id = 'formerror';
    div.innerHTML = '<b>Vul a.u.b. de volgende velden in: </b><br/>';
    for(i = 0; i < error.length; i++)
      div.innerHTML += error[i] + '<br/>';

    leftpane.appendChild(div);

    return false;
  }
  
  return true;
}