For Firefox, I use the following batch to set a configuration script:
CODE
IF NOT exists "%PROGRAMFILES%\mozilla Firefox"\defaults\pref\firefox.js echo didnt find config.file && pause && exit
echo pref("network.proxy.autoconfig_url","http://www.mydomain.de/proxy.pl" ); >> "%PROGRAMFILES%\mozilla firefox"\defaults\pref\firefox.js
echo pref("network.proxy.type",2); >> "%PROGRAMFILES%\mozilla firefox"\defaults\pref\firefox.js
exit
To make an adequate script, just make the settings in firefox and have a look, which lines are added to the prefs.js file.
Should be very similar for netscape, but we don't use it in the institute, I'm working in, anymore.