Well... there have been some issues regarding tables with width="100%" inside the CSS UNL Templates when browsing with pre 6.0 versions of Internet Explorer (Windows not Mac).
Those problems, AFAIK, have been solved.
But, problems remain for IE <=5.5 if you have content with <table style="width:100%">
Because (as is widely known) IE below 6.0 incorrectly calculates css measurements (this is known as the 'box model').
SO. We have corrected issues with width="100%" on tables inside the main pages, but I suggest you avoid inline css table width:100% unless you know how to correct it for your pages OR you don't care about IE 5.5.
And FYI, versions of IE lower than 6.0 account for about 2% of visitors.
Let me know if you notice any rendering problems within the css based templates so we can provide fixes as soon as possible.