Let me go at it from a higher level - i'm almost at a proof of concept stage for a project to see if its achieveable.
Say, for example, that due to some security restrictions a user cannot access any www site. They have an internet connection and the only "area" they will be permitted to access is abc.anysite1 The emphasis being on the "abc" prefix/URL Protocol.
This territory is fairly new to me as my background is in software development in Oracle Apps - so bear with me if my terminology is out.
I'll try to give an example from a requirements point of view:
A group of workmen are given the task of building a bridge. They are given no training and have only have their previous collective experience to work with.
Each workman is provided with a laptop with an internet connection. As this is a task that prevents them from seeking help from outside of the group, all "www" access is disabled. So the workmen are unable to access www.google.com or any www hosted website.
A new internet environment is created under an "abc" prefix where the workmen can create their own internet page, eg. http://abc.workman1, http://abc.workman2 etc. The workmen then have this "abc world" in which they can discuss their ideas in order to get the bridge built.
No one from outside of the group of workmen have access to this set of sites unless they apply to the administrator for a user-id and password to the area.
This then essentially becomes a private "World Wide Web" or "abc" , accessable to only those given access to it, which holds any forums, blogs, reference pages created by either the administrator or a workman only. The importance of their inability to access the "real" www is that they are therefore unable to see any content which they should not be seeing if you catch my drift.
This probably sounds ridiculous, but go with me on this one for a while!
You set that sort of thing up as an intranet and run it from your own computers. You would not have any internet connection for it at all unless you are just going to use the internet to provide VPN access for everyone on the intranet to be able to access your server from remote locations.