Put a label on the login page with Text="".
In PageLoad of login Page,
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
if (Session["flag"] != null)
{
Label1.Text = "You are Logged-out";
}
else
{
Label1.Text = string.Empty;
}
}
}
And,OnClick of logout button,
protected void btn_LogoutClick(object sender, EventArgs e)
{
Session["flag"]=1;
Response.redirect("Login.aspx");
}