Java developers

I am a Java newbie. I am not a student taking a class or anything, just a software developer who is trying to learn some Java on his own. I actually have my own Grand Canyon web site (www.kaibab.org) and I am trying to put together a map viewer applet to use on it.

I've got this applet that I have been playing around with and the portion that is done works fine when I run it under the appletviewer that is provided with the Sun Java SDK. When I try to imbed the applet in an HTML document it does nothing, however, and all I get is a grey box where the applet is supposed to be. I don't understand this. Shouldn't they be the same thing? Shouldn't it work the same way in a browser as in the appletviewer?

The imports that the applet is using are:

import java.awt.*;
import javax.swing.*;
import java.io.*;
import java.util.*;


Is there anything in here that would work differently or not work in the browser?

I am baffled and hoping that someone out here might be able to help.

And I SO don't like to consider myself a newbie! Having trouble with exceptions, that is, I've created my own user defined exceptions that are just supposd to display a message and go back to the main. But it dumps me out of the program once it's thrown. I think the 'catch' part is giving me troubles. anyone have any ideas? Is there something I can add to the exception itself, or what?