How to add system-wide preferences in RHEL that will take effect for all profiles.

Question

I have used the following docs to try to accomplish my task:
https://developer.mozilla.org/En/A_Brief_Guide_to_Mozilla_Preferences
https://developer.mozilla.org/en/Automatic_Mozilla_Configurator/Locked_config_settings
I wish to add proxy settings for all users, including those who already have profiles. I have tried adding to greprefs/all.js directly, using a mozilla.cfg file, all exactly as in the documents. But none of these things make a difference. Any more quidance would be SO appreciated!
I am using the latest RHEL5.5 and 3.6.13.

Answer 1

Thanks for your quick response!
I am trying the unencoded mozilla.cfg, adding these 2 lines to my all.js:
pref("general.config.obscure_value", 0);
pref("general.config.filename", "mozilla.cfg");
Here is my top-level mozilla.cfg:
//BEGIN CE prefs
// Proxy config
defaultPref("network.proxy.autoconfig_url", "http://10.10.10.10:8080/");
defaultPref("network.proxy.backup.ftp", "");
defaultPref("network.proxy.backup.ftp_port", 0);
defaultPref("network.proxy.backup.gopher", "");
defaultPref("network.proxy.backup.gopher_port", 0);
defaultPref("network.proxy.backup.socks", "");
defaultPref("network.proxy.backup.socks_port", 0);
defaultPref("network.proxy.backup.ssl", "");
defaultPref("network.proxy.backup.ssl_port", 0);
defaultPref("network.proxy.ftp", "10.10.10.10");
defaultPref("network.proxy.ftp_port", 8080);
defaultPref("network.proxy.gopher", "10.10.10.10");
defaultPref("network.proxy.gopher_port", 8080);
defaultPref("network.proxy.http", "10.10.10.10");
defaultPref("network.proxy.http_port", 8080);
defaultPref("network.proxy.no_proxies_on", "localhost, 127.0.0.1, cos.net, utmc.utc.com, doc, doc-test, scroll, scroll-test, scroll-dev, gumby, casey, crib, asic, topsweb, spiderweb, spiderweb-test, ouray, ouraydev");
defaultPref("network.proxy.share_proxy_settings", true);
defaultPref("network.proxy.socks", "10.10.10.10");
defaultPref("network.proxy.socks_port", 8080);
defaultPref("network.proxy.ssl", "10.10.10.10");
defaultPref("network.proxy.ssl_port", 8080);
defaultPref("network.proxy.type", 1);