function validate(form_id,email) {
   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
   var address = document.forms[form_id].elements[email].value;
   if(reg.test(address) == false) {
      alert('The e-mail you have entered is invalid.\nPlease try again.');
      return false;
   }
   if(reg.test(address) == true) {
      alert('Thank you for subscribing.');
   }
}