Hi
Both the java script and Regular expression validation are both in client side then why should you go for validating the email id in java script?
There is Regular expression validater for validating the Email ID.
<asp:RegularExpressionValidator ValidationExpression="^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$" ErrorMessage="Please enter a valid Email ID." SetFocusOnError="true" ControlToValidate="txtEmailID" ID="RegularExpressionValidator2" runat="server"></asp:RegularExpressionValidator>
This is will be usefull and it will reduce the stuf in using java script.
Thanks
Happy coding.