Q: How should I handle empty cells in tables?
A: Avoid empty cells that make it more complex to get an overall idea of the table structure for blind visitors. Do not use "X", "NA", "-" etc. to mark that the cell has no value. Instead, use "Not applicable", "Not available", "No value", or "Unknown" to indicate empty cells. This can be hidden to sighted readers, for instance by using white font. If one chooses to have empty cells, these should be clearly explained in the Legend/Notes under the table.