I created some new pages and subpages but in some leaf pages I need to simply present (wide) content. In order to do that I need the left pane and right pane disabled and invisible so that only the center pane is rendered. This would allow my content to occupy the entire page without a left/right column.

I don't see any option to do that. Because of this then my left pane (even though I have not added any content to that pane) shows some soft of link of the page I am viewing, my right pane is empty and my center page (about 800 pixels wide) overflows to the right edge of the page border giving it a horrible look. If I could disable (and make invisible) both the left and right panes I can make it fit as expected.

Am I missing something?

It is a standard theme. You can see what I mean with my experiment page at:

http://www.coralys.com/dental-care-and-orthodontics.aspx

As you can see the left side is being occupied by a link to the same page. Mojo does this automatically. The settings for this page are:

Parent Page:  Web Shops
Page Name:   Dental care and orthodontics
Page Title Override: <empty>
Use Url?: <checked>
Url:       ~/dental-care-and-orthodontics.aspx
Menu Icon: Page Icon
Allow Browser Caching?: <unchecked>
Include In Menu?: <unchecked>
Include In Site Map?: <unchecked>
Show Breadcrumbs?: <unchecked>
Show Child Page Breadcrumbs?: <unchecked>
Open In New Window?: <unchecked>
Show Child Pages Site Map?: <unchecked>
Hide This Page From Authenticated Users?: <unchecked>

you can also notice that the center pane content overflows past the edge of the "template" rather than expanding the center part.

but as you can see the left pane still shows a link to itself (which is rather unnecessary).

In my scenario these pages (each of the pages under the Web Shops top menu) are leaf pages. That means that they will never have children. As such I  don't need the navigation menu.

Would be handy if when one creates a page one could define whether one wants to disable (not rendered) either the left and/or the right columns. In ASP.NET when you make a panel invisible it is not rendered.

It would also be handy if one could define a bottom area that runs across all three pages and that one could use this area to add content, for example a wide banner or something like that.

In my case the suggestions don't help because I can't place these pages on the top menu so I will have to wait for the release or host them separately from the Mojo Portal (which kind of defeats the purpose of having the portal) :-(