How To Eliminate Gap Between Horizontal Menu Item Boxes

I used the CSS Menu Writer wizard to create a multi-level, vertical flyout menu with no problem. I then wanted to change the default width from 150 px to 110 px. So, I reentered the CSS Menu Writer wizard. In the Box tab, I then changed the Dimension Width from 150 px to 110 px under "Dimension, Margin & Padding". After applying the change, I now have what looks like 40 px gap between the boxes containing the menu items relative to the other boxes on the horizontal level. Of course, I want no gap between the boxes in the each row. (The vertical item boxes are still okay.)

Does anyone know how I can correct this problem? Obviously, using CSS Menu Writer is the preferred means of eliminating this gap since this is the tool I used it to create & modify the menu, and I'm trying not having to mess with the CSS or XML code directly (CSS Menu Writer generates several CSS and XML files associated with the generated menu) since using the menu wizard would be the easiest and fastest what of correcting this. However, if CSS or XML code changes are the only way, which CSS or XML related files (and item(s)) do I make the change(s) to?

Thanks in advance.