A positioned sidebar, containing a table. No problems there, as the sidebar container has a (pixel-) defined width. A main contents area, with a red border (static <div>, width defined only by margins and padding).
The tables should be as wide as the main contents, and not drop under the sidebar. Except for the first table (control table), all tables are wrapped in a div (width:100% declared).
a table, no width is declared; without a wrapper
| cell1 | cell2 | cell3 | cell4 |
| Lorem ipsum dolor sit amet, consectetuer adipiscing elit. | Aliquam ultricies, metus sed rutrum dignissim, leo dui sollicitudin sapien, | sit amet sagittis est metus ut erat. | Maecenas sollicitudin. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. |
a table, width:100% is declared, within a wrapper.
| cell1 | cell2 | cell3 | cell4 |
| Lorem ipsum dolor sit amet, consectetuer adipiscing elit. | Aliquam ultricies, metus sed rutrum dignissim, leo dui sollicitudin sapien, | sit amet sagittis est metus ut erat. | Maecenas sollicitudin. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. |
a table, width:100% is declared and equally size cells (col width:25%), within a wrapper
| cell1 | cell2 | cell3 | cell4 |
| Lorem ipsum dolor sit amet, consectetuer adipiscing elit. | Aliquam ultricies, metus sed rutrum dignissim, leo dui sollicitudin sapien, | sit amet sagittis est metus ut erat. | Maecenas sollicitudin. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. |