Carole Leita, the creator of the project, continues to oversee it. There are 44 subject areas in the top level of the hierarchy, with several hundred more subcategories in a couple of more levels. Most of the hierarchy is only two levels deep, but in some places it's deeper. In a list of subcategories, you can always identify which ones lead to more levels of subjects because they're in bold. Subjects and individual sites are sometimes listed in more than one place in the hierarchy.
Many sites also appear in two or more places in the subject hierarchy.
This practice is somewhat like a library listing a book under more than one subject heading. Sites are listed in all levels of the hierarchy. However, if the subject you're looking for sites under also has subcategories listed under it, the sites won't appear on the first page you see when you go to the subject. All of the major subject areas, and over 100 of the lower-level subjects are linked to from the main page. You can also browse an alphabetical list of all the subjects .