java plugin for firefox

[eoghan]

Hi
Does anyone have a guide or advice for getting java plugin working  
for firefox? Im running 6.1 on amd.
I have installed:
diablo-jdk-5.0
diablo-jre1.5.0
linux-blackdown-jre1.1.8
linux-sun-jdk1.4.2
when i try to access a java app from firefox im always presented with  
the plugin missing page...
I had it working on i386 before with just the installation of java...  
Im not sure what i have to do next...
Thanks
Eoghan