Bypass the need for a certificate (this howto is deprecated)

From CodeCodex



Netscape provides a way to accept a codebase as trusted (then a certificate is not needed). This can be useful during development or in a private Intranet. In the Netscape Users directory, there is a file called prefs.js. Adding the line

user_pref("signed.applets.codebase_principal_support", true);

WILL ENABLEJAR file without a certificate to request privileges on your machine. If you agree, it will be possible for an Applet to lauch a program, write a file on your hard disk or print on the printer. You will still have to ask for privileges in your program using the Netscape capabilites classes. Another way is to lower general security setting to more allow more freedom when running applets locally. Add or modify the following entries in the prefs.js:

user_pref("unsigned.applets.low_security_for_local_classes", true);
user_pref("signed.applets.local_classes_have_30_powers", true);
user_pref("signed.applets.low_security_for_local_classes", true);
user_pref("signed.applets.verbose_security_exception", true);

Then you don't need to asked for privileges for local classes. NOTE: When adding or modifying the file prefs.js, Netscape must not be running because your modification will be overwritten. So shut down Netscape, edit the prefs.js and then restart Netscape.

With IE, you can achieve the same thing through the Internet option menu.

Internet Options
Security Tab
Internet Custom level
Java permissions  
Custom radio buttons 
Java Custom settings
select the permissions given to unsigned content.

Be careful with this because this can be a huge security breach.