Basically, what Firefox did was keep the
right div floating to the right, but underneath the middle div. This
wasn’t what I wanted at all, and after about half an hour of fiddling
with the code I managed to fix it.
The Solution
All I did was cut the right div out of the code and placed it before
the middle div. It still had the same style attributes, all that was
needed was a quick swap. And hey presto! It worked!
The HTML
Change this:
<div id="left">Left Content</div>
<div id="middle">Middle Content</div>
<div id="right">Right Content</div>
To this:
<div id="left">Left Content</div>
<div id="right">Right Content</div>
<div id="middle">Middle Content</div>