1. Install Java Runtime Environment.
2. Make a symbolic link to libjavaplugin_oji.so in your Mozilla Plugins directory. Unless you are using an old version of Mozilla, or one you compiled yourself with gcc 2.9x, use the copy located in the plugin/i386/ns7 directory of JRE 5.0, or plugin/i386/ns610-gcc32 if you are using JRE 1.4.2.