Web servers sometimes behave differently for different browsers, for compatibility reasons usually, but not neccessarily.
If you want to test how a system or site behaves for different browsers, instead of preparing a lot of computers and browser installs one could try some
plugins for firefox such as the ‘User Agent Switcher‘ can help.
With it you can enter any data for the User Agent string, thereby appearing to web servers as using a browser other than the one you actually have.
The User Agent String is a text string that your browser sends with each request to tell the server what browser, operating system, extensions/plugins, etc you are using.
I didn’t initially find the format or usage of this plugin to be very intuitive, but there are importable files available online with settings for many of the more common combinations of browser/os etc.
One such list I have used is at http://qainsight.net. Check for updates to the version of the script. Right now the site is offline, but the latest (March 2008, from internet caches) appears to be here.
Last I read it does not properly cater for the different User Agent String formats of other browsers, for instance the IE and Firefox string are quite different in both content and organisation. So while it will usually work, it may sometimes fail, and will probably not hide the fact of what browser you are actually using from those who might really want to know…