A user interface architecture wherein user content and user interface are composed of documents with links is described. User content documents and user interface documents are both displayed in a single viewing frame. A non-linear navigation history is maintained such that a user can navigate along a first path, back up using a previous link, navigate along a second path, back up along the second path using the previous link, and re-navigate along the first path again using a next link. Every document page to which a user navigates is saved in the user's navigation history. Users can query their navigation histories and view their navigation histories in various ways. Users can access, annotate, and customize the user interface in the same manner in which users access, annotate, and modify user content documents.