By default, all newly created pages are private and unaccessible by non-logged in visitors. World readable rights have been set up on a few pages (lab presentations, people and contract lists, all publications,…) in order to present a nice pubic site. As a rule of thumb, it is advisable to have at least one publicly readable page for each user/contract/group to give a brief overview to the anonymous visitor.
It may be wise to create an ACL group per namespace (e.g. ACL group lara-com for LaRAcom's pages) if fine access control is desired.
Currently, it is not possible for normal users to change ACLs. Once you've decided which of your pages and namespace should be publicly viewable (or, on the contrary, not accesisble to some logged-in users), please contact one of the administrators (everybody who is an administrator for this wiki should include tag admin on their user page) who will happily help you.