Why my validation summary not show after i click ligin button in my login control. It supposed to show an error message if i leave it blank in username n password box right? Can you guys tell me what should i do? 

   <asp:Login ID="Login1" runat="server" BackColor="#F7F7DE" BorderColor="#CCCC99"
                            BorderStyle="Solid" BorderWidth="1px" Font-Names="Verdana" Font-Size="10pt">
                            <TitleTextStyle BackColor="#6B696B" Font-Bold="True" ForeColor="#FFFFFF" />
                        </asp:Login>
                    </p>
                   <asp:ValidationSummary ID="ValidationSummary1" runat="server"
    ValidationGroup="Login1" />