The Origin of Tabbed Browsing
As filing goes digital, more and more images of old files reappear. The memory of these systems of categorization must be brought up again in order to create the new systems. In fact, the systems of filing are never new; to be the most efficient, digital systems must do the work of the old, in a way that is visually similar to the old.
Hence 'tabbed' browsing. It's the most efficient and memorable way to browse, and gives the feeling of depth. It looks just like real-life manilla 3 tab files used for important documents.