Rated 4 out of 5 stars

If you simply want to search within the current page or host, and to save the room space of your screen.

You may try Search Everywhere.

https://addons.mozilla.org/en-US/firefox/addon/5054

This review is for a previous version of the add-on (1.0.6). 

Toolbar is optional

The toolbar is optional and can be hidden if one doesn't want to use it (view->toolbars->site search).