If you see the applet but it does not work properly, you may be running an incompatible version of Java. The applet has been tested under Windows Vista with JRE version 6 update 13 and various later versions, and under Windows 7.
Regrettably, each new version of Java seems to cause more problems for the applet and I am not always able to correct them, not having access to the source code. You can install older Java versions here.
Also be aware that the applet may not scale properly when the page is zoomed in or out on your browser. For best results, view it at the default size.