First: Abandon Nvu. Download KompoZer
instead. The name change is for legal reasons only. It offers a significant range of bug fixes. There is no reason for using Nvu these days.
Second: Do NOT consider using tables for page layout. Such techniques are more than a decade out of date.
Instead use CSS to style your content and place it exactly where you want on the page. Find out how to do this from the "KompoZer by Example" section of this forum. My site also offers some help for newcomers to KompoZer.