how the user be logged in even if he closes the browser...

private void ValidateLogin(string emailAddress, string password)
{
try
{
UserInfo objUserInfo = null;
objUserInfo = Gateway.Users.ValidateLogin(emailAddress, password);

if (objUserInfo == null || objUserInfo.UserID == 0)
{
lblError.Text = IEC_Common.Messages.MSG_INVALID_USERNAME_PWD;
trErrorMsg.Visible = true;
return;
}

//if (!IEC_Data_Access.DatabaseUtility.ValidateLogin(emailAddress, password, ref objUserInfo))
//{
// lblError.Text = IEC_Common.Messages.MSG_INVALID_USERNAME_PWD;
// trErrorMsg.Visible = true;
// return;
//}

LoginManager.LogInUser(objUserInfo);

// Create the cookie that contains the forms authentication ticket

HttpCookie authCookie = FormsAuthentication.GetAuthCookie(emailAddress, true);

// Get the FormsAuthenticationTicket out of the encrypted cookie

FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(authCookie.Value);

// Create a new FormsAuthenticationTicket that includes our custom User Data

FormsAuthenticationTicket newTicket = new FormsAuthenticationTicket(ticket.Version, ticket.Name, ticket.IssueDate, ticket.Expiration, ticket.IsPersistent, "");

// Update the authCookie's Value to use the encrypted version of newTicket

authCookie.Value = FormsAuthentication.Encrypt(newTicket);

// Manually add the authCookie to the Cookies collection

Response.Cookies.Add(authCookie);

// Determine redirect URL and send user there

string redirUrl = FormsAuthentication.GetRedirectUrl(emailAddress, chkLogin.Checked);

//if (!redirUrl.Contains("MENU_ID="))
//{
// redirUrl += "?MENU_ID=35";
//}

Response.Redirect(Navigation.GetTamperProofURL(redirUrl));

}
catch (Exception ex)
{
lblError.Text = ex.Message;
}
}


this is my code