If you saw a message that said "Inactive Plug-in" when you wanted to play a Java applet game or something, turn on the Java applet plug-in for browsers. It's vary easy.
- Launch "Java Preferences". You can find it by using Spotlight.
- Check "Enable applet plug-in and Web Start applications".
- Re-start your browser. That's it!
The update to OSX Lion 10.7 would disable Java applet in browsers for some reason.
