19. Why does the map have a large orange square in the middle?

That was a big virtual stack of bounding boxes of identical extent. Each one corresponds to a "neighboring" place that falls within the same Barrington Atlas grid square as the place; the map is designed to show you the current page's place resource in blue and neighboring places in brownish-orange. When the 16,000+ coordinate pairs assembled by the DARMC project are integrated into Pleiades, many of these boxes will disappear (reappearing as discrete points in the proper location). Other bounding boxes will remain, indicating to users that precise coordinates are still needed for these places (consider it an invitation to submit content to Pleiades!).

Update (October 2011): "Was" is emphasized in the paragraph above because the map interface has changed considerably since the question was first posed. Roughly located neighboring places are now collected into an object depicted as a cloud that hovers around the place of interest.