I already told you about Maclife’s instructions on how to disable Java on your Browsers. There is an additional step you can do to keep Java from running altogether on your Mac. Lion, doesn’t come with Java pre-installed, so this will only apply to those running an OS version earlier than Lion, or who downloaded Java from Apple after upgrading to Lion last summer.
Go to the Applications Folder, look for the Utilities Folder and inside that folder you should find the Java Preferences. app. Open it and make sure the following boxes are unselected:
That should do it, do this, do what Maclife says on disabling Java on the browser, install all Apple and browser updates, be careful on the internet and you should be OK.