You can look at the Classic Theme Restorer extension to restore some functionality that was lost wit

You can look at the Classic Theme Restorer extension to restore some functionality that was lost with the arrival of the Australis style in Firefox 29.

Classic Theme Restorer: https://addons.mozilla.org/firefox/addon/classicthemerestorer/

You can check the settings of the CTR extension via its Options/Preferences button on the "Firefox/Tools > Add-ons > Extensions" page.

Firefox 29 and later versions have the Australis interface that looks different than the user interface in Firefox 28 and older versions.

With the Australis interface the orange Firefox menu button has been replaced by the three bar Firefox Menu button at the far right end of the Navigation Toolbar
A consequence of this new menu button is that you no longer can hide the Navigation Toolbar

There is a star like button to the right end of the search bar on the Navigation Toolbar to bookmark the current web page and a "Show your bookmarks" button next to it to open the Bookmarks in a drop down menu

It is still possible to have the menu bar visible via the right-click context menu on the toolbars to have menus like the the Bookmarks menu

See also:

https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox

https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox

https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox

http://forums.mozillazine.org/viewtopic.php?f=38&t=2824649