cascading menu causing extra space at bottom of page

[hannah]

I am using a javascript cascading menu that is causing a lot of extra space to appear at the bottom of the page. However, when you move your mouse over one of the main menu items, the page "readjusts" to the proper height, just under my lowest table. I've put a simplified version of the problem at:
http://www.floridashirdisai.org/csi/templates/parenttest.htm

I would really appreciate any help on removing this extra space.

Thanks so much!

Hannah