This is another commandline trick.

First to set the Proxy settings we need to edit the file called all.js in the greprefs folder and find the line that starts with proxy.type. Here is how to do this...

1. When logged onto the machine as an admin user open the Terminal and type..

sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /Applications/Firefox.app/Contents/MacOS/greprefs/all.js

This will open the all.js in textedit, search for the string "proxy.type" (Press CMD+F) and change it to look something like this. Just replace your relevant information...

pref("network.proxy.type", 1);
pref("network.proxy.ftp", "YourIPAddressToProxy");
pref("network.proxy.ftp_port", 8080);
pref("network.proxy.gopher", "YourIPAddressToProxy");
pref("network.proxy.gopher_port", 8080);
pref("network.proxy.http", "YourIPAddressToProxy");
pref("network.proxy.http_port", 0);
pref("network.proxy.ssl", "YourIPAddressToProxy");
pref("network.proxy.ssl_port", 0);
pref("network.proxy.socks", "YourIPAddressToSocks");
pref("network.proxy.socks_port", 0);
pref("network.proxy.socks_version", 5);
pref("network.proxy.socks_remote_dns", false);
pref("network.proxy.no_proxies_on", "localhost, 127.0.0.1, .yourlocal.domains");

Now to set the Home Page

To do this we need to edit this file....

sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /Applications/Firefox.app/Contents/MacOS/browserconfig.properties

The file by default looks like this...

browser.startup.homepage=http://en-US.start.mozilla.com/firefox?client=firefox-a&rls=org.mozilla:en-US:official
browser.startup.homepage_reset=http://en-US.start.mozilla.com/firefox?client=firefox-a&rls=org.mozilla:en-US:official

Just change the URLs in there to reflect your desired default homepage for any account on the machine.