Firefox aids your searches by auto-filling suggested sites based on your bookmarks and browsing history below your search bar.This can be an overwhelming form of assistance particularly if you have many bookmarks and a voluminous browsing history. Fortunately, you can refine this search using the following modifiers
^ for matches in your browsing history
* for matches in your bookmarks
+ for matches in pages you’ve tagged
% for matches in your currently open tabs
~ for matches in pages you’ve typed
# for matches in page titles
@ for matches in web addresses (URLs).
Syntax: <keyword> <space> <modifiers>
Note: You can also use multiple modifiers(with space in between) in same search itself.