Email ID Validation

 <script type="text/javascript">

              function validate() 
                {
            var mailid = document.getElementById('<%=txtmailid.ClientID%>').value;

             var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;


              if (mailid == "")
              {

                alert("Please Enter Mail ID");
                return false;
              }

            if (!reg.test(mailid)) {
                alert('Invalid Email Address');
                return false;
            }