Firefox – How to disable address bar search option in Firefox

I couldn't access subfolders in my wamp www directory through Firefox 12.0 a few days ago by typing this in the address bar:

http://localhost/folder/subfolder

Firefox 12.0 starts Google search when I press ENTER, and I tried a workaround to disable address bar search by doing this:

about:config -> keyword.URL ; set the string as none. 

Now I can access the subfolders. I know it is not the proper way to do it, but I'd like to know if somebody has a better idea.