[Typo3] redesigning layout

[Puddin Taine]

I'm sure there's a place in the doc where this is covered, but I'm
not finding it (and no, I haven't ruled out selective blindness).  I
have gone through some of the tutorial, made modifications to the
sample Bigfeet site, and so become (very) basically familiar with
how to add/modify content in a few different ways.

The fundamental layout of the Bigfeet site includes a vertical stroke
at the left, and a horizontal stroke near the top, which divide the
page into four quadrants, the Northwest quadrant being quite small
(where the Bigfeet logo goes) and the Southeast quadrant being much
larger (where the bulk of the content goes).

What if I want to change that?  What if I want, e.g., 

  - a banner completely across the top, 

  - a menu bar below that (but beginning partway across the page, that
    is, not all the way to the left), 

  - a large image (roughly) centered horizontally below the menu bar,

  - some links on the right, 

  - and some text below the image?

I'm not asking how to make this exact layout (though that'd be great),
just how to make changes like this, and where the best doc is on it.

Thanks.

-PT