Denegar pegar link en navegador

[lbauerle]

protected void Login1_Authenticate1(object sender, AuthenticateEventArgs e)
{
xxxxx.Usuario u = new xxxxx.Usuario(Login1.UserName, Login1.Password);
e.Authenticated = u.Autenticado;
if (e.Authenticated)
{
FormsAuthentication.SetAuthCookie(u.UserName, false);
Request.Cookies.Add(new HttpCookie("UserName", u.UserName));
FormsAuthentication.RedirectFromLoginPage(u.UserNa me, false);

StringBuilder popup = new StringBuilder();
popup.Append("<script>");
popup.Append("window.open('defaults2.aspx','_blank ','toolbar=0,location=0,menubar=0,resizable=0,widt h=1366,height=768,top=5,left=5,scrollbars=1');");
popup.Append("</script>;");
Response.Write(popup);


SIN EMBARGO, ME ABRE EL siempre el webforms seteado en el control login1:

BorderPadding="2" DestinationPageUrl="~/Defaults.aspx" onauthenticate="Login1_Authenticate1"



q esta mal?