Facebook Connect error page how to fix

when i click to facebook connect button and my website is go to this link

Code:

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Only registered members can view the code.

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and get ERROR 404: Requested page not found Undefined Page

how to fix it

Hi Kornsin,
I just checked your website and was unable to reproduce the problem, the Facebook Connect button works well.
Have you fixed it already?

John

i have same problem on http://www.ugostiteljskaburza.hr/
worked fine and suddenly blank page or 404