Kindly help me in understanding this:

Suppose I'm working with: <http://graph.facebook.com/cocacola>

<http://graph.facebook.com/cocacola/feed> was working but today its returning "An access token is required to request this resource."

Did the page owner changed something on it? If I'm the page owner how can I make it available without access token and how can I make it require the access token?

Thank you in advance