Javacript: void (0).....how the hell do I fix it?

I’ve been to a few sites that require javascript to run. Java is enabled, but I’m getting a lot of “javascript: void (0)” errors. What is it that needs doing to get websites to work again? I’ve tried updating Java but the Java website says initially that I’ve got an old version of Java, but when I process the suggested download and run it, it says that the version I’m trying to install already exists.
I’ve run numerous scans to see if I can pick up any other problems with malware or viruses but nothing shows up.
Any ideas?