You'd need to remove the blank table cell element entirely, and change the colspan attribute on another cell in the row to encompass the released space, e.g.:
refToCellToRemove.remove();
refTocellToExpand.colspan = 4;
Note that setting it via setAttribute (which would otherwise be correct) will not work properly on IE.
Beware: IE does some very strange table layout things when you muck about with colspans dynamically. If you can avoid it, I would.