Security :: Logout Action In IE?

I have a login page and a default page to be redirected to after login. when I clicked on thew logout button in the default page it correctly redirects to login page. But when I click the back button in the IE I can again see the protected default page( in mozilla everythng is OK, no problem but in IE this problem occurs).

Have I done something wrong. My code r below:

login page===========

protected void Login1_LoggedIn(object sender, EventArgs e)
{
if (Roles.IsUserInRole(Login1.UserName, "Members")) {
Response.Redirect("users/Member/default.aspx");
//Server.Transfer("users/Member/default.aspx",true);
}
}
===========

default page has a LoginStatus button( logout action: RedirectToLoginPage)