It is interesting to know that Mozilla provides a mechanism for us to lock any preferences in the option menu. If you would like to play with it, follow these instructions:
1. Go to Tools > Options...
2. Change the setting of the preference you want to lock.
e.g. lock General > Home Page Location to "about:blank".
3. Open "about:config" to find the key of the preference. Use the filter field to save your time from scrolling up and down.
e.g. Type in "homepage" and you can find "browser.startup.homepage".
4. Open a notepad and write in the following lines:
//
lockPref("browser.startup.homepage", "about:blank" );
5. Save it as Mozilla.txt and do byte shift with an offset of 13. Use this byte shift service. You will receive a file "mozilla.cfg", which you must save it at the location of firefox.exe.
6. Add the following line to "C:\Program Files\Mozilla Firefox\greprefs\all.js" file:
pref("general.config.filename", "mozilla.cfg" );
You will find your homepage field in options uneditable after that.
A tester...