function validate_email() {
   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
   var address = document.getElementById("email").value;
   if(reg.test(address) == false) {
      alert('Invalid Email Address');
      return false;
   }
}