facebook sdk authorization on multiple pages

var auth = ne开发者_如何学JAVAw CanvasAuthorizer();
            auth.Permissions = new[] { "user_about_me" };

            if (auth.Authorize())
            { get needed data...

If i place this code in default.aspx (Page_Load method), it works fine. If I place this in a viewscore.aspx (Page_Load method), Authorize() returns false. I get to viewscore.aspx by using a link from default.aspx, nothing special. Why is this difference?

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I'm not sure, but doesn't Facebook allow canvas authorization only on page which has been given as a Canvas URL?