Facebook 400 Bad Request with login_status.php (with Facebook Canvas Iframe Application) - include appropriate FeatureLoader.js ex> http://static.ak.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php (O, for F8 canvas iframe) http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php (X, for F8 connect app??) - cross domain channel file (xd_receiver.htm)s URL should have Application Setting - Connect - Connect Url as PREFIX ex> http://yourdomain.com/xxx/xd_receiver.htm ==> Connect URL should be http://yourdomain.com/xxx/