Logout Button is not working properly

public partial class Home : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        if (!IsPostBack)
        {
            Label1.Text = (string)Session["username"];   
        }
        
       
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        Session.Abandon();
        Session.Remove("username");
        FormsAuthentication.SignOut();
        
        Response.Redirect("Default.aspx");

    }
}