function popup(url, w, h, name)
{
  if(name == null) name = '';
  var x = Math.round(0.8 * screen.width) - w;
  var y = Math.round(0.2 * screen.height);
  window.open(url, name, 'left=' + x + ',top=' + y + ',width=' + w + ',height=' + h + ',scrollbars=no');
}

function rollover(name)
{
  var img = document.images[name];
  if(img == null && document.getElementById) img = document.getElementById(name);
  var src = img.src;
  img.oldsrc = src;
  var dot = src.lastIndexOf('.');
  img.src = src.substr(0, dot) + '_over' + src.substr(dot);
}

function rollout(name)
{
  var img = document.images[name];
  if(img == null && document.getElementById) img = document.getElementById(name);
  img.src = img.oldsrc;
}

function preload(src)
{
  var img = new Image();
  img.src = src;
}

function chkEmpty(field, msg)
{
  if(field.value.search(/\S/) != -1) return true;
  alert(msg);
  field.focus();
  return false;
}

function chkEmailDe(field)
{
  if(field.value.search(/^([A-Za-z0-9_\.+-]+@([A-Za-z0-9-]+\.)+[A-Za-z0-9-]+)?$/) != -1) return true;
  alert('Ungültige Emailaddresse');
  field.focus();
  return false;
}

function chkNewsletterDe(form) {
  return (
    chkEmpty(form.addr, 'Bitte gib Deine Emailaddresse ein!') &&
    chkEmailDe(form.addr));
}

function chkEmailEn(field)
{
  if(field.value.search(/^([A-Za-z0-9_\.+-]+@([A-Za-z0-9-]+\.)+[A-Za-z0-9-]+)?$/) != -1) return true;
  alert('Invalid e-mail address');
  field.focus();
  return false;
}

function chkNewsletterEn(form) {
  return (
    chkEmpty(form.addr, 'Please enter your e-mail address') &&
    chkEmailEn(form.addr));
}