Press Ctrl+B and a new pane appears on the left side of your Firefox browser: The Bookmarks pane. Your cursor will automatically appear in the search box. Type in a few letters, and only those pages you’ve bookmarked that include those letters are listed. Press Tab to jump down to the results, and then press Enter on the one you want to open. Press Ctrl+B again to toggle off the Bookmarks pane.
(Note that in Internet Explorer, Ctrl+B lets you organize your bookmarks.)