Java problem with gamesville

We just purchased an iMac on Sun and this is basically the first time I've used one. I've got tons of experience with a PC so this is driving me crazy!

When I try to load gamesville.com games I get this message:
Your version of Java is not able to render Gamesville games correctly. Why? This may be because of recent updates to your computer, or your computer may not have been equipped with Java in the first place. Fortunately, the resolution is simple:

Install the free Java Virtual Machine
After installing, close your browser, start it up again, and return here; everything should work just fine

According to my computer there are no updates available......what should I do?

Thanks in advance!!
Please remember to talk to me in stupid terms since I new to this crazy backwards mac!