In my Default.aspx I'd like to have the logout button only show if the user is logged in, so:

<div id="login_style" class="user" runat="server" visible='<%# User.Identity.IsAuthenticated %>'>
...

If I put this in the skin, all is well, and the login/logout buttons don't show.  But if I put it in Default.aspx, User.Identity.IsAuthenticated seems to always return "true".  What am I missing here?

Thanks for the heads-up. I honestly hadn't considered that. All the same, for this project the decision has already been made to customize default.aspx. So the question remains, why does User.Identity.IsAuthenticated return a different value in default.aspx than in the skin file?