Configure Sun's Java Plugin for Firefox

1. Install the JRE or JDK as RPM or in your favorite location;
2. Open a shell and go to: ~/.mozilla
3. 64-bit platform: create the link: ln -s /opt/java/jdk1.7/jre/lib/amd64/libnpjp2.so . (the dot stands for the current directory)
4. 32-bit platform: search for the directory: i386.

Reference:
http://www.java.com/en/download/help/index_installing.xml