It is a very powerful public service for locating information on the Web quickly and reliably, and probably the best resource of its kind. Additional pages are added to the hierarchy as necessary to ease navigation.
Most features are available to non-forms users, but searching requires a browser with forms support.
The content has no particular focus, but spans numerous fields of interest. Selected links are then evaluated by index administrators and placed into the subject hierarchy as appropriate. Both the hierarchy of the subject index and the layout of the search page are very simple. Navigation across the hierarchy is very fast, with a peppy response time. There are very few dead links on the server, and the administrators regularly remove links to outdated pages.