Modify Firefox settings on the Web

"Firefox Profilemaker is an online tool that enables you to make configuration changes to Firefox by exporting those changes either to a Firefox profile or saving them as a prefs.js file instead for existing profiles.
"The idea is very similar to that of ConfigFox, a third-party program for Firefox that provides you with options to configure security, privacy and other Firefox settings which in turn is based on our privacy and security settings listing for the browser.
"The online tool walks you through seven configuration pages, each listing a distinct set of features and options to either enable or disable it. ..."
Source: gHacks Tech News
 Firefox Profilemaker: modify Firefox settings on the Web