as gtamil says it will add border width to each column. So the options for yuor, as I see them, are: 1) do as he says 2) remove 1px from each column that has a 1px border 3) use background images, not the actual borders
Option 3 is usually my preference, since I usually want the delimiters to be equal in height. I would have a background image on a container-container (not div columns) that repeats vertically. If you want to use this method, but do not have dividers of equal height, you can add the same image to the columns.
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