Almost all linux distros does not come with Java plugin in their browsers. Although you install Java separately from Synaptic or from other sources, you will be surprised to see that Java application would work but no applet or java enabled site would work properly on your browser. In Windows we typically install Java addon which fixes this issue.
Solution
The automatic Java plugin in Firefox on Linux will fail all the time, so you have to manually install the plugin to get it working. Install ‘icedtea6-plugin‘ to get over the problem. Note: For OpenJDK 7 users, you need to install icedtea7-plugin.
sudo apt-get install icedtea6-plugin
firefox java ubuntu install Java Plugin for Ubuntu and other Linux distros
