This applet works differently in every browser, but most of these differences aren't important. I've tried this applet on various machines I have access to, and it seems to run decently on HotJava (Solaris), Opera (Win95), Internet Explorer (Win98, and MacOS 9), and Netscape 4.7x (Win95, Win98, and Linux). It does not run entirely properly on Netscape 4.6x on Linux and Solaris: the "Calculating" animation doesn't work, and the graphs do not reset when the Run button is pressed. I suspect this has something to do with the Java runtime included with this version of Netscape.
The more serious problem occurs on MacOS 9. On Netscape 4.7x for OS 9, this applet will not load: the status bar says that ParrondoApplet.class cannot be found. I don't know why this happens, but I will try to fix it. Internet Explorer on OS 9 seems to work. I haven't had a chance to try the simulator on OS X.
If anybody out there has any insight into these problems, please email me.