The latest version of Silverlight is required by the demos on this website. A plugin download link is provided as needed. Silverlight supports a variety of browsers on Windows and Intel powered Macs, but is not available for PowerPC Macs. Linux users need to wait for Moonlight.
On Windows, current versions of Safari and SeaMonkey seem to be compatible with this website's Silverlight applications, despite their lack of official support by Microsoft. I haven't tested the website with SeaMonkey on OS X.
On rare occasions, earlier versions of Chrome failed to load Silverlight 3 content, which could only be viewed after reloading the page, or clearing the cache and relaunching the browser. Hopefully the issue does not exist with the current versions of Chrome and Silverlight.
Opera has numerous incompatibilities with this website. Browsing the Silverlight applications with Opera is an entertaining adventure, especially when done in a side by side comparison with another browser.
Silverlight compatibility is not the only requirement for a web browser to be usable on this web site. A certain level of compliance with web standards is also necessary, so versions 6 and below of Internet Explorer do not work here. IE 7 is not supported either, but it will work if you can tolerate some ugliness. An upgrade to the latest version is strongly recommended.