Moving a div to bottom

positioning div box model question

[boheme]

Hi all! I've got a simply div positioning question:

I have the next html code (only relevant code)

<div id="wrapper">
 <div id="first">foo1</div>
 <div id="second">foo2</div>
</div>

both div first and second have variable height.

I know, using css, how to make the next things:
1.- display foo1 first than foo2 in this way:
foo1 foo2
2.- display foo1 after foo2:
foo2 foo1
3.- display foo1 first than foo2 vertically:
foo1
foo2

And the question is:
¿How can I make foo2 display first than foo1 vertically?
foo2
foo1

Thanks all!

[your_store]

deleted.. missed the fact both divs had varying heights.

[boheme]

I think that maybe it's not possible to do.