"expand" area to show hidden object

I have a div that is hidden until someone checks a checkbox. The problem is, it leaves a big white space while that div is hidden. How do I make it so that the content under the hidden box fits neatly under the content that is showing, and then after they check the box, everything shifts to make room for the hidden div??

I have no idea where to start with this, but I've seen something similar when downloading the latest Acrobat Reader.

instead of:
visibility: hidden
and:
visibility: visible
use:
display: none
and (not sure on this one):
display: inline

It might not be inline, it could be normal or block too. just test and see what it is.

Div is generally a block element, so you might want to set it display: block;

Thanks for that one Jop