Rule #10: Avoid using nested table structures.

Using nested tables for complicated layouts seems easy and sensible, but they are impossible to maintain, difficult for another developer to read, and detrimental to accessibility by people with disabilities. Nested table layouts amount to a trial-and-error process, rather than a consistent user-interface coding technique.

Things to Do Instead

• Consider using <div> and <span> in addition to tables as formatting blocks of content, or even instead of them. Nesting <div> and <span> tags is fine. You need to brush up on you CSS to do this, these tags don't have all the formatting attributes that a <td> does.
• Compose your pages of stacked, shorter tables.
• Change your design to something simpler to format.

Legitimate tabular data, such as one record or record set, should all be contained in one table.