After days of research. insert excuse text... yada yada. I have yet to be able to successfully authenticate. Essentially, My aspx redirects to the facebook login page and does not redirect back. I'm assuming it's a setting problem in me application on me facebook developer account.
My settings look like this. I'm assuming that the [Post-Authorize Redirect URL] setting should be the same as the page that I am on in my web application that is redirecting to with the following line.
step 1. http://www.domainname.com/messagesend.aspx page is navigated to in browser.
step 2. server code in message.aspx hits this line of code
Response.Redirect(@"http://www.Facebook.com/login.php?api_key=" ...
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