Language negotiation
The whole website uses a feature of the Hypertext Transfer Protocol, the language negotiation.
When your browser requests a page, it specifies the language(s) you want with a quality factor. This information is usually not used, but some websites like this one do take it into account. You can change the language(s) in your browser's preferences.
Since some browsers like iCab only offer one language and some users don't choose either French or English and because sometimes the settings cannot be changed, each page has a little flag to change the language. This setting is saved for all the session thanks to a parameter in the URL.
If you have Newtscape 2.0-v2 or later, you can change this setting in i:General:Other Option:Accept-Language. Put en; q=1.0, fr; q=0.5 for choosing English as preferred language and French as second choice.
For a change, Netscape (at least Netscape 4.6 for MacOS) doesn't respect the standards or doesn't do what it says it does. Indeed, the language order in the preferences only changes the language order in the Accept-Language header, Netscape doesn't use the quality factors. And yet, the RFC 2616 explains that the order shouldn't be taken into account and that only the factors matter.
But since this kind of very well written software are rather widespread, this website takes the order into account. Please note that this site is nevertheless compliant. Indeed, the choice of the language when the request doesn't explicitly says which one is preferred is left to the server.
Monique Neubourg kindly sent me a screenshot for Internet Explorer. On the contrary to Netscape, Explorer (at least MSIE 5.0 for Macintosh) is RFC 2616 compliant.
You simply need to indicate the languages in the order you wish in the "Language / Fonts" preference panel.