Keep in mind that the option to `Always show the tab bar` needs to be checked. Otherwise, the orange Firefox menu button will overlay the navigation bar if you are only viewing one page, and you won't be able to click on it until another tab is opened.
Also, here is a link to CSS code that, in addition to pushing the tab bar up, makes the orange menu button look much nicer:
http
/www.downloadsquad.com/2010/07/06/remove-stuck-firefox-4-orange-menu-button-css/