It would be a good idea to tell us what version of Suse you're using, so we would have a better idea of how to help you.
But for Suse 11.3, install Sun Java from Yast, don't do it the hard way from the link you provided. Yast > Software Management > Search tab, type in java then look for java-1_6_0-sun and java-1_6_0-sun-plugin. It will install them for you and put the plugin in the correct directory.
The directory for the FF plugins is /usr/lib64/browser-plugins fro 64 Bit, or /usr/lib/browser-plugins for 32 Bit.