If you just upgraded your Mac to OS X Mountain Lion you probably noticed that Java Runtime Environment (JRE) is removed from your system. Apple has decided that Java is unnecessary for OS X and Mountain Lion upgrade process uninstalls Java but you can install it afterwards.
Apple theoretically tries to reduce the risk of security problems with Java just like we saw few months back with Flashback Trojan which infected over 700,000 Mac computers.
OK, got it working now, short & sweet 2-step process for how to make Java work under 10.8:
1) From your terminal, run
you will get a Mac OS X dialog asking to install Java SE 6, click 'Yes'
2) From your browser, run
you will get a Mac OS X dialog asking to enable Java plugins, click 'Yes'
How to Install Java in OS X 10.8 Mountain Lion | Print Screen Mac
Why Java is removed after upgrading to OS X Mountain Lion and how to reinstall it. If you just upgraded your Mac to OS X Mountain Lion you probably not