So it appears this mysterious blank area is symply the background image of the table, which defaults to a tansparent (?) area in case no background image or color was specified.
As a test, I added this line to the Xiangqi Scans button of my Interactive Diagram that is further down in the comments:
The result I got in Safari on my iPad was that it showed the board only at the top, and it showed the pieces below the board without a background image.
As a test, I added this line to the Xiangqi Scans button of my Interactive Diagram that is further down in the comments:
getElementById('board0').style.backgroundRepeat='no-repeat'The result I got in Safari on my iPad was that it showed the board only at the top, and it showed the pieces below the board without a background image.