form validation example
<div class='form-group'>
<label class='control-label' for='EmailAddress'>Email address *</label>
<asp:TextBox ID="EmailAddress" runat="server" CssClass="form-control" placeholder="Email" ClientIDMode="Static"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator" runat="server" ControlToValidate="EmailAddress" ErrorMessage="Please Enter Valid Email Address" ForeColor="Red" ValidationExpression="^\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$"></asp:RegularExpressionValidator>
</div>