Which is better for a z-index, auto or numbered? Are there specific instances when one should take precedence over another?
Also, I am noticing that the order in which you place the DIV tags makes a difference when the CSS is turned of. Even though I thought I was design from Top-down things seem to place themselves whereever they want when css is turned off. I'm a little confused there. I have had to put things logically out of order in the web page to make things look right when css is off. Why is that?
Use z-index if you want to set one. The default is that content later in the document goes ontop of content earlier in the document. There are some cases where Mozilla does not understand this though, so if you are specifically putting content ontop of other content, then you'll want to do it explicitly.
The order when css is off is the same order as your code.