function isValidEmail(currentForm){
  validRegExp = /^[^@]+@[^@]+.[a-z]{2,}$/i;
  strEmail = currentForm.email.value;
  //strEmail = document.forms[currentForm].email.value;

   // search email text for regular exp matches
    if (strEmail.search(validRegExp) == -1) 
   {
      alert('Bitte geben Sie eine gültige E-Mail-Adresse an.');
      return false;
    } 
    return true; 
}