question about log-out and form authentication

 Hi
I have this website created with c# which uses forms authentication and has this login page and member pages , in web config i have
<forms protection="All" timeout="120000"  requireSSL="false" slidingExpiration="true"
               cookieless="UseCookies" enableCrossAppRedirects="false" loginUrl="~/Login.aspx" />
and in login.aspx
public partial class Login : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Membership.ValidateUser(UserName.Text, Password.Text))
        {
            FormsAuthentication.RedirectFromLoginPage(UserName.Text, RememberMe.Che ...