So you need to have these and you should know that. When Facebook declares: xmlns:fb="http://graph.facebook.com/schema/og/" This mean that they define a "folder" in which their custom tags/attributes/properties are stored, so: As the important part is "fb:admins" and when it is the same as having this on your hard drive: /fb/admins.txt So it contains the USER_ID value. So it's just a way to keep data organized and separated.