I'm trying to manually install the java plugin for Firefox4 on maverick (got ff4 from the PPA), but it seems the usual instructions don't work. I've tried doing both
cd ~/.mozilla/plugins ln -s $JAVA_HOME/jre/lib/i386/libnpjp2.so .
cd /usr/lib/firefox ln -s $JAVA_HOME/jre/lib/i386/libnpjp2.so .
but I still get the "missing plugin" warning in Firefox. Used to work fine for firefox 3.6. Also, after doing the first above chromium is able to pick up the java plugin without problems. In case it makes any difference I'm running Oracle's "vanilla" JDK, not the Ubuntu