I cannot for the life of me get java to work in Firefox and thought I'd ask someone for help.

Can someone please tell (or link) me how to make java work in Firefox?

*I've read the this link but it didn't work.
*I've tried Icedtea from the package manager (w/plugin) and when java is about to load I get an error message.
*I've tried Suns java (w/plugin), but nothing loads
*I've downloaded from java.com and tried linking myself, but it doesn't work. I can't even find my firefox's plugins folder.
*I've tried playing around with links in /usr/, /usr/lib/, /usr/lib/browser-plugins, /etc/alternatives and probably a lot more that I can't remember now.
*I've tried update-alternatives --config java, but it doesn't seem to help

Perhaps worth mentioning is that my colleague installed the KDE version while I opted for Gnome. His java (icedtea?) worked out of the box, while mine gave an error.

Can someone help, pretty please?