Creating Website Thumbnails

Hi

Basically I am trying to create thumbnails of websites when passed the
URL. So far I have used this:

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;

class ScreenCapture {
  public static void main(String args[]) throws
           AWTException, IOException, InterruptedException {
     // capture the whole screen
      String[] cmd = { "C:\\Program Files\\Mozilla Firefox\\firefox.exe",
"http://www.facebook.com" };
      Runtime.getRuntime().exec(cmd);
      Thread.sleep(1000);
      BufferedImage screencapture = new Robot().createScreenCapture(
           new
Rectangle(Toolkit.getDefaultToolkit().getScreenSize()) );

     // Save as JPEG
     File file = new File("screencapture.jpg");
     ImageIO.write(screencapture, "jpg", file);

     // Save as PNG
     // File file = new File("screencapture.png");
     // ImageIO.write(screencapture, "png", file);
  }
}

This more or less captures a screenshot of firefox with the webpage
open. Currently I have used Thread.sleep(1000) as a delay for the
webpage to load in FireFox before a screenshot is taken. Is there any
way Firefox or IE can callback to the java app when the webpage loads?

P.S I am a Java novice, so be nice :P

Cheers

Lawrence