Force divbox to move down, if other divbox expand

Force divbox to move down, if other divbox expand

Hey,

look at this fiddle http://jsfiddle.net/CW7uF/4/

I want that if i go e.g. on "Main 1" and the div2 expands the other "Main Tabs" slide down and you can fully see the div2

I just tried to do that with

div1 ---> position: relative; but dosnt work

Any idea why this dosnt work?