<SCRIPT LANGUAGE="JavaScript">
function validateEmail(obj) {
var re = new RegExp("^[a-zA-Z0-9 -()@,'.]*$");
var txt = obj.value;
if (txt.match(re)) {
alert("Successful match");
} else {
alert("No match");
}
return false;
}
</SCRIPT>
<asp:TextBox ID="email" runat="server" onblur="return validateEmail(this);"></asp:TextBox>