What is 'a valid next URL' on Facebook?

I keep getting this error: "Requires valid next URL" while trying 开发者_运维百科to redirect to that adress: http://www.facebook.com/authorize.php?api_key=API_CODE_HERE&v=1.0&ext_perm=read_stream&next=http://apps.facebook.com/my-app-name/

I have also tried replacing 'http://apps.facebook.com/my-app-name/' with 'http://my-app.com' but hasn't helped either.

So what shall I put in 'next' in that adress?

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Ok, fixed it myself. Just used login.php instead of authorize.php and 'req_perms' instead 'ext_perms'