what safari did, is to automatically add "www." and ".com" to wrap anything you typed in between, this won't work with any url ended with .net or .org, etc.
By default, firefox will only do this when you press cmd+enter. Otherwise, firefox uses google, or google feeling lucky search, so you might see google search result, or you might be taken to the top result of google result directly.
Firefox will first try to send your request to a keyword search service. By default, this service is Google's Browse by Name service. For example, If you type mozilla foundation into the Location bar, Firefox will submit a query to the Google Browse by Name service, since this is not a valid URL. The service will direct you to its best match for your request, and direct you to http://www.mozilla.org. An entry without a clear match to a URL will display search results for the entry.
for changing these settings, you can go here
http://support.mozilla.com/nl/kb/location+bar+search
basically you just turn off
keyword.enabled in
about:config, after which it will behave as safari does.
You can also specific what prefix and suffix firefox should add, by changing the pref of
browser.fixup.alternate.prefix and
browser.fixup.alternate.suffix