For Windows and Mac OSX the procedure is straight forward. Some steps are given below for installing the Java plug-in on Linux:
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner" sudo apt-get update sudo apt-get install sun-java6-jdk sudo apt-get install sun-java6-plugin
Manual Installation and Registration of Java Plugin for Linux: http://www.oracle.com/technetwork/java/javase/manual-plugin-install-linux-136395.html