Well, for a "quick fix"...
right after you middle div...
add a non breaking space...
<div id="middle">
Of course, it would help if you had a Doc Type, had a 0 (zero) for padding rather than an O (Capital letter o) etc. etc.
Pelase...
http://validator.w3.org
Use it to check as you build, saves lots of annoying little confusions.