It looks like a combination of two issues were causing this problem. One is that this diagram had rank and file markers around it, and I haven't done anything to adjust the height and width of the table cells with the rank and file markers in them. The other is that I was using cqi and cqb values in browsers that were apparently treating these units as zero. So, when I first got rid of the file and rank markers, the whole board disappeared on Chrome in my Android phone and on any browser on the iPhone. When I removed the cqi and cqb values from the min function, the board showed up in these browsers at an appropriate size. I still have to fix things for when a board includes rank and file markers, but for now, I have omitted them from this board, and it is displaying properly on phone displays.
It looks like a combination of two issues were causing this problem. One is that this diagram had rank and file markers around it, and I haven't done anything to adjust the height and width of the table cells with the rank and file markers in them. The other is that I was using cqi and cqb values in browsers that were apparently treating these units as zero. So, when I first got rid of the file and rank markers, the whole board disappeared on Chrome in my Android phone and on any browser on the iPhone. When I removed the cqi and cqb values from the min function, the board showed up in these browsers at an appropriate size. I still have to fix things for when a board includes rank and file markers, but for now, I have omitted them from this board, and it is displaying properly on phone displays.