How do I alter Java security?

[OldAstrologer]

This is not really a programming question -- I'm not a programmer and don't want to be one -- but I suspect only a programmer can answer.

I'm trying to access on-line journals via a library computer, but the Java (1.7) plugin for Firefox (2.0) won't accept the applet from the library server:

java.security.AccessControlException: access denied
(java.net.SocketPermission appserve.londonlibrary.co.uk resolve)
at java.security.AccessControlContext.checkPermission (AccessControlContext.java:342)
at java.security.AccessController.checkPermission(Acc essController.java:556)
at java.lang.SecurityManager.checkPermission(Security Manager.java:550)
at java.lang.SecurityManager.checkConnect(SecurityMan ager.java:1049)
at java.net.InetAddress.getAllByName0(InetAddress.jav a:1192)
at java.net.InetAddress.getAllByName0(InetAddress.jav a:1173)
at java.net.InetAddress.getAllByName(InetAddress.java :1120)
at com.citrix.client.io.net.ip.s.a(Unknown Source)
at com.citrix.client.io.net.ip.s.a(Unknown Source)
at com.citrix.client.module.td.tcp.TCPTransportDriver .t(Unknown Source)
at com.citrix.client.module.td.TransportDriver.run(Un known Source)
at java.lang.Thread.run(Thread.java:675)

Someone suggested
cat << EOC > $java.policy
grant codeBase "http://appserve.londonlibrary.co.uk" {
permission java.security.AllPermission;
}
EOC
but that doesn't help. The hundreds of files in /usr/share/javadoc are incomprehensible and ten pages of Googling produced nothing.

Does anyone have a solution, please?

[OldAstrologer]

The answer, if anyone else has a similar problem, turns out to be inserting

grant codeBase {
permission java.security.AllPermission;
};

into the file java.policy manually; the command line trick I was given doesn't work in Fedora.