You know... I've never gone picking through the Preferences/Options with Firefox, but I bet that's the place to look. IE is notorious for looking different on every system you view it on.
I've never looked back since switching from IE, which I only switched
to when Netscape (my standby for years) went a bit crazy a few years ago and created an "upgrade" that was not only Bug City but also wanted to be much more than a browser. [Note to browser developers: I don't want to be part of your bloody
community, I just want to see web pages!
]