If you install blackdown-jre and firefox, you still cannot use java with firefox, because the symlink in /usr/lib/MozillaFirefox/plugins is missing! You need to do this: emerge blackdown-jre cd /usr/lib/MozillaFirefox/plugins ln -s /opt/blackdown-jre-1.4.2.01/plugin/i386/mozilla/libjavaplugin_oji.so javaplugin_oji.so enter about:plugins in firefox -> it works :)
you need to merge blackdown-jre with mozilla useflag (soon to be renamed to browserplugin or something)
Oooh, uuuhm...sorry :)