It is a typo in the documentation that there should be three. there are only two.
The outcome of following that tutorial is to create a layout with a wider header area, and a navigation bar below it.
Since the rounded corners designs are image based, you cannot simply use the controls in CSS Sculptor to add a new div and have that div use rounded corners. You need to first make the layout in an image editing program, then create the slices to be used in CSS Sculptor.
There are a number of people who have been able to successfully follow the tutorial, in all honesty, this is the first time the issue has been raised.
Aside from the mistake of mentioning three images when there are only two, is there specific part of the tutorial you are falling down on?
