function validateEmail (emailField) {
 emailpattern = /^([a-zA-Z0-9])+([\.a-zA-Z0-9_-])*@([a-zA-Z0-9])+(\.[a-zA-Z0-9_-]+)+$/;
 if( !emailpattern.test( emailField.value ) ) {
  alert("Please enter a valid email address");
  emailField.focus();
  emailField.select();
  return false;
 }
 return true;
}