The node with ID 1 is the real root node, under which the content root node, users root node, media root node are placed. Node 1 doesn't contain any object.
If you don't want your users to be able to read other objects (and relate them to your articles), then you can just remove the vertical arrow button in content/browse when the can_read attribute of the parent node is false.
If you want your users to be able to browse the node with id 1, then assign content/read permissions for it:
- content/read without any restrictions - manually add content/read node(node with id 1) to your database, this seems not possible through the admin interface.
