If you use the Google Toolbar like I do then that is where you store access to all of your bookmarks. The FireFox web browser is set up by default to provide a bookmarks toolbar which if it is not used then its a waste of space. Initially it looks like the bookmarks toolbar is just part of the FireFox design however by simply unchecking the Bookmarks Toolbar as shown below in the image you gain more room for the display of web pages.
The Bookmarks Toolbar can be turned off by clicking View in the top navigation, selecting Toolbars from the drop down menu, and then selecting Bookmarks Toolbar from the side menu. Make sure the Toolbar does not have a checkmark next to it.
As you can see below when you are on a 12.1 inch laptop monitor any little extra space can make a big difference.
With FireFox Bookmarks Toolbar On:
Without FireFox Bookmarks Toolbar On:
Again even though its minimal any extra browser window space is beneficial