Thanks for your feedback Shai.
I'm using the zen theme.
Drupal themes typically have sidebars. Out-of-the-box Drupal installations can easily populate the sidebar or sidebars with information put in custom blocks or blocks generated by modules. The main content column is typically populated by data coming from nodes (stories, pages...).
Is there a way in which you can have the sidebars running underneath the header, navigation and "content_top" regions? I couldn't find a way in which to do this.
It seems like you aren't asking about anything more complex than what comes out-of-the-box in Drupal.
I'm now trying to assign two new "regions" - content_bottom_left and content_bottom_right
If and when you do need more complex page layouts, one popular module is called Panels (http://drupal.org/project/panels). Just be warned though, Panels is powerful and flexible but also pretty complex to use. It would be better getting experience building simpler Drupal installs first before beginning to fuss with panels.
I looked at Panels but it doesn't have a Drupal 6 version - otherwise it sounds like it would have ben ideal.
I've just changed my .info and page.tpl.php and I can now assign blocks to these two new regions. However I need to change the style sheet somewhere in order to have them display side-by-side rather than one on top of the other.
Any ideas where and how and where I do this?
Thanks,
Marc