function check_email() {
  var email = document.newsletter.email.value;
  pattern = new RegExp( '^([a-zA-Z0-9\\-\\.\\_]+)(\\@)([a-zA-Z0-9\\-\\.]+)([\\.])([a-zA-Z]{2,4})$' );
     if ( !pattern.test(email) ) {
       alert("E-mail address is not valid !");
   	   document.newsletter.email.focus();
	   return false; }	
  document.newsletter.submit();
}