Javascript Function to validate EmailId

<script type="text/javascript">
    function validateEmail(emailField){
        var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;

        if (reg.test(emailField.value) == false)
        {
            alert('Invalid Email Address');
            return false;
        }

        return true;

}
</script>


<asp:TextBox ID="txtemail" runat="server" Width="150px" onblur="validateEmail(this);"></asp:TextBox>