program works but wont display in browser

I wrote a small picture viewer in java and tha program runs but after I put
it online I get a null pointer exception. Not sure why since it compiles and
runs fine otherwise.
Can someone please point me in the right direction.

Thank You,
Andy

//Web Page
//By: Andrew Titus
//Date 2-26

import javax.swing.JApplet;
import java.awt.Event;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.util.*;
import java.awt.*;
import javax.swing.ImageIcon;
import java.awt.event.*;
import javax.swing.*;


public class WebApplet extends JApplet
{

private JButton previous,next;
private JPanel buttonPanel;
Image coolImage[] = new Image[5];
Font title,documentText;
int i = 0;

String[] names = {"StBasials1.jpg", "museum9.jpg", "Red_Square9.jpg",
"StBasials8.jpg",
"Russian_Soilders_in_Formation.jpg" };


public void init()
{
previous = new JButton("Previous");
next = new JButton("Next");

for(int j=0; j<names.length;j++) {
coolImage[j] = getImage(getCodeBase(),names[j] );
}


ButtonListener listener = new ButtonListener();
previous.addActionListener(listener);
next.addActionListener(listener);

buttonPanel = new JPanel();

buttonPanel.add(previous);
buttonPanel.add(next);


add(buttonPanel);

} // end init()



public void paint(Graphics page)
{
setBackground(Color.black);


title = new Font("Jokerman",Font.BOLD,(int)(getHeight()*0.02) );
documentText = new Font("Courier New",Font.BOLD,(int)(getHeight()*0.02) );

//set color for text
page.setColor(Color.white);
page.setFont(title);


page.setFont(documentText);


page.drawImage(coolImage[i],30,60,this);

} //end paint()

private class ButtonListener implements ActionListener
{
public void actionPerformed (ActionEvent event)
{
if(event.getSource() == next){
i++;
repaint();
}
if(event.getSource() == previous) {
i--;
repaint();
}
}

}


} //end webApplet
.