My installation of Mozilla 1.0.1 didn’t come preconfigured to be able to load Java applets. So I found Hogarth’s Mozilla Reference to help configure it. The directions are for a Debian system, but I had no trouble adapting it to my RedHat 8 system. I already had Java 1.4 installed, so I skipped that step. Then I just created a symbolic link for the plug-in library:
ln -s usr/java/j2sdk/jre/plugin/i386/ns610/libjavaplugin_oji.so /usr/lib/mozilla-1.0.1/plugins