This site has three primary requirements. The first is a modern, (reasonably) standards compliant browser. This may include Firefox, Mozilla, and Internet Explorer 6.
The site also requires the Apple QuickTime VR plug-in for viewing the virtual garden. This is available for free at http://www.apple.com/quicktime/download/.
Lastly, It is beneficial, though not necessary, to have a current version of the Macromedia Flash plug-in. This will allow you to navigate the garden via an overhead map. This is available for free from Macromedia. For more information, visit http://www.macromedia.com/go/getflashplayer.