I'm using a technique similar to this, now, and am being told by
someone that it crashes their browser.

Here's my code:

import java.applet.*;
import java.awt.*;

public class ShowInfo extends Applet
{
   String output = "", javaVendor, javaVersion;

   public void start() {
       try {
           javaVendor = System.getProperty("java.vendor");
           javaVersion = javaVendor.startsWith("Microsoft") ?
System.getProperty("java.version") :
System.getProperty("java.vm.version");
       } catch (Exception e) {
           //e.printStackTrace();
       }
   }

   public void paint(Graphics g) {
       g.drawString(javaVendor,10,25);
       g.drawString(javaVersion,10,50);
   }
}

I tried it, myself, on IE6 with MSJVM 1.1 and FF2 with Sun JVM 1.5 and
both worked.  I don't know what browser their using nor do I know the
JVM vendor / version (that's what this script was supposed to find
out...)

Any ideas?  Maybe I should be using something more like what Arne
Vajh?j posted?