hello...
well - you can do a few things - one would be to pick a height that would allow for all of your various content and then make sure you keep the content within the length to fit in your pre-defined space for it on each section. otherwise, you would need to implement scroll bars within your layout to allow overflow of content but not affect the overall height. you could do the latter with either an iframe or a div with an overflow property...
here's an iframe example i've used around here before:
http://sitruc.com/cow/iframe/iframe.html
and here's a discussion of a div with an overflow property set:
http://www.quirksmode.org/css/overflow.html
hope that helps!
sitruc