Short question but long answer.
Many people do use tables for the layout of their page. In fact, even professional sites often to this (probably as it's relatively easy to achieve).
However, mbanners is correct: tables should not be used to influence overall page layout, as that is not what a table is for. It's for displaying tabular information.
One of the alternatives is frames, but let's not go there: frames are a prime "usability crime".
The preferred method of page layout is use of CSS to position <div> elements, which become the containers for your content. This is slightly more complex that using tables, but worthwhile learning.
If you decide to stick with tables, there's no reason to have a table with a single cell for the banner - just have the banner. Then for the 2nd half of your page a single table split into two cells would do fine. Plus, of course, you are free to place tables within tables within tables. (Another reason not to use tables for page layouts: it cna get messy quickly with all those td and tr tags all over the place.)
Here's a basic example of a site where the content is split up using div tags and css styling:
divTest3.html