You are right, in regard to CSS, but making the width declaration directly as opposed to putting it in a CSS selector does change some behavior.  (<TD width="200">  as opposed to <TD Style "WIDTH:200;">.  It's not supposed to be like that but try it in different browsers., particularly with how empty cells collapse (or not).

I had to go back and futz around with one of my skins for an answer - but basicly this is what happens.  If a TD width is specified using CSS, the cell will retain that width regardless of whether there is any content in the cell.  If the width is declared within the tag, the cell will collapse if there is no content within it. 

When I first started working with skinning, my goal was to create skins using 100% CSS.  I tried to create a basic template with designs that could be radically changed using only CSS (like Zen Garden).    I found that is was possible to create some simple skins like that, but  for any thing with multiple content panes there were way too many problems..  After many, many hours of trial and error, I gave up, Now I style as much as I can using CSS, but also have to rely on tables and inline HTML both for consitant behaviour between browsers and for the control that I need.