div block size different in IE Firefox ?!?

Hi,

I'm trying to use DIV instead of tables for positioning objects on the
page.
It was great till I realized that IE sizes DIVs differently from
Firefox.
Please see example at:
http://www.polidora.com/test.html

The sidebar should be 200px wide, but Firefox is making that larger.

What am I missing ?
I'm going crazy...

thanks for your time,
-GianLuca

Arne,
thanks for your kind reply.
I posted the example just a couple of minutes after my post.
You should see it know, and yes, there is a full Doctype declaration.
The different div size is very apparent.
The image is 600px, and the DIV should be 200px.
-Gian

I'm really sorry, but didn't you -we- write the very same declaration
?!

Ok. Arne was right, and *his* declaration does produce the same output
on IE/FF.
Thanks.
Thanks you both for your kind help.
-Gian