This demonstrates a small subset of the features of the Weather Wizard. There is no GRIB, no routing, no possibility to save anything.
But that gives you a taste of the possibilities.
The applet is signed. That means it wants to get out of the Sun sandbox. Namely, it wants to read the faxes from an external website.
Once you have selected your composite (from the top drop-down list), do not forget to hit the "Go" button...