If you are on a webpage that is running a Java applet and the thing isn’t running [or just won’t work right!], these instructions from http://www.math.ucsd.edu/~crypto/fixjava.html may help.

How to Fix Java Applet Security Errors

Security Errors When Loading Java Applets

Did you get errors like the following when you tried to run a Java applet in the web browser?

Your Java version is out-of-date.
Application Blocked
Application Blocked by Security Settings
Your security settings have blocked an application from running with an out-of-date or expired version of Java.
Your security settings have blocked an untrusted application from running.

For security reasons, recent versions of Java may block unsigned Java applets from automatically running by default.

Solution #1

If you are allowed to install/upgrade software on your computer, please install the latest Java upgrade first, relaunch the web browser, and try again.

Solution #2

If you are unable to install/upgrade to the latest Java version, and you trust the unsigned Java applet to be safe, you can workaround this problem by adding an “exception site” or temporarily lowering the security level of the currently installed Java:

For Microsoft Windows:

1. Click on the Windows “Start” menu in the lower-left corner of the screen –>
   “Control Panel” –>
   “Programs” –>
   “Java”.
2. In the “Java Control Panel” window that appears –>
   Click the “Security” tab.
3. If there is a “Exception Site List” section in this window, click on the “Edit Site List…” button –>
   Click the “Add” button –>
   Type in the web server location for the Java applet like “http://www.math.ucsd.edu/” –>
   Click the “OK” button –>
   Click the “OK” button.
4. If there is no “Exception Site List” section in this window –>
   Slide the “Security Level” indicator from “High” down to “Medium” –>
   Click the “Apply” button –>
   Click the “OK” button.
5. Close ALL of the open windows. You must completely QUIT the web browser or this workaround will fail.
6. Re-launch the web browser.
7. Go to the Java applet.
8. When the “Security Warning” window asking “Do you want to run this application?” appears, if there is a “I accept the risk and want to run this app.” option, checkmark it ON first then –>
   Click the “Run” button.
9. The Java applet should load OK now. You may need to click on it to start it.
10. When you are done using the Java applet, you should change the Java “Security Level” back to “High” if you had lowered it down to “Medium” earlier.

For Mac OS X:

1. Click on the “Apple” menu in the upper-left corner of the screen –>
   “System Preferences…” –> “Java”.
2. In the “Java Control Panel” window that appears –>
   Click the “Security” tab.
3. If there is a “Exception Site List” section in this window:
   click on the “Edit Site List…” button –>
   Click the “Add” button –>
   Type in the web server location for the Java applet like “http://www.math.ucsd.edu/” –>
   Click the “OK” button –>
   Click the “OK” button.
4. If there is no “Exception Site List” section in this window –>
   Slide the “Security Level” indicator from “High” down to “Medium” –>
   Click the “Apply” button –>
   Click the “OK” button.
5. Close ALL of the open windows. You must completely QUIT the web browser or this workaround will fail.
6. Re-launch the web browser.
7. Go to the Java applet.
8. When the “Security Warning” window asking “Do you want to run this application?” appears, if there is a “I accept the risk and want to run this app.” option, checkmark it ON first then –> Click the “Run” button.
9. The Java applet should load OK now. You may need to click on it to start it.
10. When you are done using the Java applet, you should change the Java “Security Level” back to “High” if you had lowered it down to “Medium” earlier.