function checkform(form)
{
  //Primitieve Javascript form checker v0.01a
  //Kay Maatkamp http://kaydies.com/
 
  //De 'no-check' class op een form element
  //slaat deze over.

  var inputfields = ["text", "password", "textarea"],
    buttons       = ["radio"],
    elements      = "",
    error         = -1,
    error_message = "";

  for (var x = 0; form.elements[x]; x++) {

      var element = form.elements[x];

    if(element.className.indexOf("no-check") >= 0) {
      error = -1;
    }
    else if (buttons.indexOf(element.type) >= 0) {

      error_message = "U heeft niet alle velden ingevuld."
      error = x;

      for (i = 0; i < form.elements[element.name].length; i++) {
        if (form.elements[element.name][i].checked) {
          error = -1;
        } else if (!form.elements[element.name][i].checked) {
          error = error != -1 ? x : error;
        }
       }
    }
    else if (inputfields.indexOf(element.type) >= 0) {

      if (element.type=="text" && element.className.indexOf("email") >= 0) {

        error_message = "U heeft geen geldig e-mail adres ingevuld."
        var reg = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

        error = !reg.test(element.value) ? x : error;
      } else if (element.value == "") {

        error_message = "U heeft niet alle velden ingevuld."
        error = x;

      }
    }
    if (error != -1) break;
  }
  if (error > -1) {
    alert (error_message);
    form.elements[error].focus();
    return false;
  }
  return true;
}

//This prototype is provided by the Mozilla foundation and
//is distributed under the MIT license.
//http://www.ibiblio.org/pub/Linux/LICENSES/mit.license

if (!Array.prototype.indexOf) {
  Array.prototype.indexOf = function(elt /*, from*/) {
    var len = this.length;
    var from = Number(arguments[1]) || 0;
    from = (from < 0) ? Math.ceil(from) : Math.floor(from);
    if (from < 0) from += len;
    for (; from < len; from++) {
      if (from in this && this[from] === elt) return from;
    } return -1;
  };
}