In the Facebook developer area where you created your application, make sure the Sandbox Mode setting, in "Settings -> Advanced" is not enabled.
Then, you should be able to visit your application page at:
www.facebook.com/apps/application.php?id=12345
Where 12345 is the Application ID for your Facebook App.
I'm not sure why that link wouldn't work, but hopefully the above will get you going!
Thanks,
Alex