Hi,
Sounds like a couple of things…
First, is your “sidebar” intended to be a sidebar in the true sense (widgetized and all that stuff)? Maybe what you want is a horizontal element that contains only a horizontal navigation list of categories. In that case you can create a horizontal nav list using the wp_list_categories tag, and configure and style it as you wish.
Alternatively, you CAN make a sidebar horizontal if you wish, but you have to style it to be across the top rather than on the side.
To make your nav list horizontal in either case, identify the class or id of your nav list, and add display: inline; to it in your stylesheet. This will make the list display across the top rather than descend to the bottom.
Access this link for that and everything you want to know about horizontal nav menus.
Hope this helps…
Sure sounds like I have a lot of homework on my hands tonight!
Highly appreciated for this content.