"Why not read a document in its native form, as a tree? Directory trees, for example, are best viewed and navigated with "tree controls" (like the Windows Explorer): you see a vertical list of top-level directories, and opening one inserts its contents below and indented. Items there can themselves be clicked to open their contents in place, and so on all the way down, without ever hiding the top-level stuff you started with. Everything appears in place, and nothing gets erased." Ooooooooooooh. This looks exciting and, more importantly, brain-dead easy to use.