Like the previous post, this is a Java applet bundled up into a ".jar" and hosted at docs.google.com. I find I can see the crab in Firefox, Internet Explorer and Chrome on Windows XP (SP2) and Windows 7. I haven't yet been able to get it running in Safari (OS X) or Firefox/Chromium (Ubuntu amd64 - probably a plug-in issue).
In the comments please let me know whether you see a crab and what browser/OS you're using.
(It seems that I can't view the applet from any browser that's logged in to my docs.google.com account. Probably a security measure to protect users from self-modifying applets.)