Firefox Search Box Tip

If you use Firefox, you know there’s a handy little web search box in the top-right corner.  And hopefully you know that you can press the Ctrl+K shortcut combination (on Windows) to put focus in the search box.  You hit Enter to run the search in the current tab or Alt+Enter to run the search in a new tab.  But did you know that you can press Ctrl+Up / Ctrl+Down to change the target search engine?