As you can see from my original image (in the question), I have no borders between the cell columns. I used border-right-color: none
This seems to be the reason. Instead, I changed it to border-right-color: White (to match the border with the background color), and the columns are now fully aligned with the column headers.
Perhaps this was a problem with IE, as it worked correctly in Chrome even before the change.
Ron harlev
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