Website Logout after some time?

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ASM

I use login control and logout control from tool control.when
user login and working in site then it automatically logout.

my login code

SqlParameter[] paramater = new SqlParameter[]
              {                              
                  new SqlParameter("@User_Name",Login1.UserName),
                  new SqlParameter("@Password",Login1.Password)                               
              };
            SqlDataReader dr = (SqlDataReader)db.ExecuteReader("Login", paramater);
            if (dr.HasRows)
            {
             FormsAuthentication.RedirectFromLoginPage(Login1.UserName, false);
             Response.Redirect(@"~/Home.aspx", false);
            }

In web config

<authentication mode="Forms">
<forms loginUrl="~/LogIn.aspx" protection="All" slidingExpiration="true" timeout="2880"</authentication>

At masterpage

protected void Page_Load(object sender, EventArgs e)
   {       
       if (!HttpContext.Current.User.Identity.IsAuthenticated)
       {
          Response.Redirect("~/LogIn.aspx");
       }
}
protected void HeadLoginStatus_LoggedOut(object sender, EventArgs e)
    {
        FormsAuthentication.SignOut();
 Response.Redirect(@"~/Login.aspx", false);
    }

pls help its urgent and i cant solve it..check is it write or not..