follow steps below (only for linux 32 bit systems)
1. Download bin file from the link below:
2. chmod 0777 jdk-6u45-linux-i586.bin
4. mv jdk1.6.0_45 /opt/
5. cd /usr/lib/firefox-addons/plugins
6. ln -s /opt/jdk1.6.0_45/jre/lib/i386/libnpjp2.so .
7. close firefox and restart firefox
to checkj add on is added or not
open firefox -> options -> add-ons -> Plugins
check javaTM(plugin is installed or not ? upgrade it if you want to upgrade )
if you are not able to make This plugin Always activate then Follow the steps below
How to set old versions of plugins to 'Always Activate'?
1. open firefox
2. open about:config (have to enter 2-3 times to open it)
3.this will list configurations of firefox
4. Look for '' and set it to false
5. This will remove the 'is known to be vulnerable message and enable the previously greyed out 'ask to activate' & 'Always active' options.
You can then set the plug in to always enable by setting the relevant value for ':
0 - Never Active
1 - Ask to Active
2 - Always Active
I saw 'plugin.state.java' & 'plugin.state.ndeployjava' when looking during my testing.