Appying border

Hi all, quick question:

I have built a webpage, and have applied a: <div id=“wrapper”> at the top of my body, and the end tag, </div> at the bottom of my body to encompass my entire page. I then apply a border to the #wrapper to cover my page. In IE, the border works fine, but in FF it only wraps around the first few divs, ignoring the remainder of the page. After some fiddling about, I’ve realized If I remove all <div class> from my page the border will work in FF. For some reason it doesn’t like the <div class> in the middle of my page.

Any idea why, or how to overcome this problem? I need to keep all <div class>'s.

Thanks in advance,