The Search field in Firefox allows you to quickly search for a specific term using different search engines. It's a useful feature as it is, but the Inquisitor extension takes it to a whole new level. Once installed, it lets you perform searches using multiple search engines at the same time.

When you enter a keyword in the Search field, Inquisitor displays a pop-up window containing a list of matching Web sites as well as a list of keyword suggestions. Inquisitor uses Yahoo! as its default search engine, but you can change that by tweaking the extension's options. To do this, choose Tool -> Add-ons and press the Preferences button next to the Inquisitor extension. Here you can change the default search engine to Google as well as enable the multi-engine search. To do the latter, tick the Display links to additional search engines check box and press the Edit Sites button. To add a new engine, press the Add button and select the engine you want from the list of available search sites. If the desired engine is not on the list, you can add it manually by selecting the New custom search shortcut menu item. Give the added engine a name and enter the search URL using the <TERM> variable as a search term placeholder. For example, if you want to add the Cambridge Dictionary search engine, do a search and note the resulting URL which looks like this:

http://dictionary.cambridge.org/results.asp?searchword=monkey

Replace then the search keyword with the <TERM> variable:

http://dictionary.cambridge.org/results.asp?searchword=<TERM>

This is your search URL which you can use in Inquisitor.