Excellent (and long) article here that covers most of the frequently-asked-for tweaks and hacks to about:config in Firefox.
I had originally found it while trying to remember how to tweak my Firefox so that when I type in a keyword string into the address bar, it would send me to Google search results, instead of Google’s “I’m feeling lucky”. And sure enough, I found exactly what I was looking for – and tons more – in this article:
You may have noticed that if you type something into Firefox’s address bar that’s not an address (a “keyword”), Firefox typically passes it on to Google as an “I’m Feeling Lucky” search term. The exact search engine string to use is defined in the string preference keyword.URL; if you want to change it to something else, you can simply edit this string.
So I changed it to a normal Google search results string, and voila.
Even though this article was written in 2007, most of the info still applies, so its still a worthwhile article to check out. Computer World: Hacking Firefox: The Secrets of about:config