Save UserName and Password, but how?

On the Login control there is a checkbox to save the username and password.

But it never works, so how could i make it work ?
This is the code of it:

<asp:Login ID="Login1" runat="server" BackColor="#F7F6F3" BorderColor="#E6E2D8"
         BorderPadding="4" BorderStyle="Solid" BorderWidth="1px"
         DestinationPageUrl="~/Default.aspx" Font-Names="Arial"
         ForeColor="#333333" CreateUserUrl="~/login/createUser.aspx" OnLoggedIn="Login1_LoggedIn" OnLoggingIn="Login1_LoggingIn" OnAuthenticate="Login1_Authenticate" CreateUserText="Registreren" PasswordRecoveryText="Wachtwoord vergeten?" PasswordRecoveryUrl="~/login/passwordRecovery.aspx" FailureText=&quo ...