Dorothy,
Ok... let me explain a little something here. =)
Yes, as you mentioned "ClassNotFound" is a pretty popular, very generic Java exception. Every time an applet you run calls for a class, and for ANY reason at all doesn't get access to it, you get a "ClassNotFound" error. So there literally can be a million reasons why this happens. Only one of these reasons is your Java installation being faulty, which I think we've now well and truly established is not the problem.
But that is also the reason I couldn't really give you a suggestion as to what you should do, I can only give you some very generic suggestion. As I asked before, does this happen only on a specific website? While trying to run a specific applet? One possibility is that the applet you're trying to run is simply buggy. In that case you'll just have to contact the website's tech support. Another common issue is when you're sitting behind a proxy that doesn't let the applet run properly. Disable whatever internet security software you have and see what happens. [And try a different browser too, while you're at it.]
Another possibility is a version conflict. If you, like many of us, are running a combination of 32-bit and 64-bit browsers on a 64-bit operating system, you may need to install both the 32-bit and the 64-bit versions of Java for everything to run properly.
Let me know if any of this makes a difference. =)
Cheers!
Nov 7, 12 01:59