Magento: MagentoDesignGuide.pdf, exercise 1 on page 45
===

I am following the Magento Design Guide (MagentoDesignGuide.pdf)
downloade from the following official site:

    http://www.magentocommerce.com/design_guide/

    On page 45 of the guide, I can do Exercise 1, where it says
    _In the category page_, move the "My Cart" box from the right
    column to the left. I have flushed and disabled the magento
    cache, otherwise this would not have worked at all. When I
    complete the exercise, I do not see the shopping cart on
    the right unless I click on, say, "Furniture", "Electronics",
    or "Apparel", as supplied by the sample data.
    
    So, my question is, having filled out layout/checkout.xml, how
    come if I set <reference name="right"> the shopping cart area
    shows up in all pages, whereas with <reference name="left">
    shows up only on some pages but not on all. Where do I read
    this functionality from the supplied magento layout and
    template files that define the current design package and theme?
    
    Why does the cart appear on the main page if we set name="right"
    but not if we set name="left"?

Thanks,

John Goche