function launchFull(url, name, height, width) 

{
  var str = "height=" + height + ",innerHeight=" + height;
  str += ",width=" + width + ",innerWidth=" + width;
  if (window.screen) 
  {
    var ah = screen.availHeight - 30;
    var aw = screen.availWidth - 10;

    var xc = (aw - width) / 2;
    var yc = (ah - height) / 2;

    str += ",left=" + xc + ",resizable=no,menubar=no,locationbar=no,status=no,scrollbars=yes,screenX=" + xc;
    str += ",top=" + yc + ",screenY=" + yc;
  }
  window.open(url, name, str);
}


function newImage(arg) {
	if (document.images) {
		rslt = new Image();
		rslt.src = arg;
		return rslt;
	}
}

function changeImages() {
	if (document.images && (preloadFlag == true)) {
		for (var i=0; i<changeImages.arguments.length; i+=2) {
			document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}
}

var preloadFlag = false;
function preloadImages() {
	if (document.images) {
		home_over = newImage("images/btn_rentonline_over_en.gif");
		home_over = newImage("images/btn_rentonline_over_nl.gif");
		preloadFlag = true;
	}
}

function checkform ( form )
{
  // see http://www.thesitewizard.com/archive/validation.shtml
  // for an explanation of this script and how to use it on your
  // own website

  // ** START **
  if (form.email.value == "") {
    alert( "Bitte geben Sie Ihre e-mail-Adresse an." );
    form.email.focus();
    return false ;
  }
  if (form.name.value == "") {
    alert( "Bitte geben Sie Ihren Namen ein." );
    form.name.focus();
    return false ;
  }
  if (form.telefon.value == "") {
    alert( "Bitte geben Sie Ihre Telefonnummer ein." );
    form.telefon.focus();
    return false ;
  }
  // ** END **
  return true ;
}