The tabular stylesheet generates HTML where the navigation markup appears before the content. This means that a visually impaired person using using a screen reader has to listen to the entire list of navigation links before hearing the main content of a page. This problem also affects users of non-graphical browsers such as Lynx.
There is a simple technique known as the "table" trick which enables content to be presented first in the HTML, while still keeping the navigation on the left hand side. The table trick is documented in http://diveintoaccessibility.org/day_10_presenting_your_main_content_first.html and http://www.apromotionguide.com/tabletrick.html