So here's how to install Sun's Java Plugin for Firefox 3.6.x and above.
1. First, install Sun's JDK.
2. After installing the JDK successfully, try to locate the file libnpjp2.so , by using the locate command:
[rhythm@mybox ~]$ locate libnpjp2.so
Take note of the result of the command, in this case, it's /usr/java/jdk1.6.0_20/jre/lib/i386/libnpjp2.so
3. Become root by executing the following command.
su4. Make a link to the libnpjp2.so file on the mozilla plugins folder using the following command, please replace the text "location of the libnpjp2.so file" with the result of the command executed on step 2.
ln -s "location of the libnpjp2.so file" /usr/lib/mozilla/plugins/libjavaplugin.so
In my case, since the result of the command on step 2 is /usr/java/jdk1.6.0_20/jre/lib/i386/libnpjp2.so , the command will be:
ln -s /usr/java/jdk1.6.0_20/jre/lib/i386/libnpjp2.so /usr/lib/mozilla/plugins/libjavaplugin.so
5. Restart Firefox.
There you have it, now, the java plugin should be available on the list of plugins when you access Tools -> Add-Ons -> Plugins. Enable it if it's still disabled, and you should be ready to go! Please comment if you encounter any problems with this. Thanks to wenlong for the info!