How to maintain height of panel on webpage in case of dynamic controls visibility onto it and maintain footer position according to them??

I am using a panel on the web form to hold some more hidden panels onto it.

But when I am making those hidden panel visible panel size remains same and footer goes down and page looks ugly then.

How to maintain size of panel as well as footer w.r.t. it?

Please reply asap, its urgent!!

Thanks! :)

KGProgrammer