To get the menu, you need to hit your device's menu button.

that's the problem. On my Toshiba AT 105 running 4.0 there is no menu symbol on the bottom bar. Have never had this problem on any other app, including Dolphin.

Press the three dot/bar button on the right of the address bar.

This sort of menu is common on Android 4.0+ for example the Gmail, Youtube and Google+ apps uses this menu design.

Look at the far right end of the navigation bar and find the downward pointing triangle. It's located between the star, for Favorites, and the circular arrow, for Refresh.

Right click on the triangle, and in the drop down list that appears you'll see that Menu Bar is unchecked. Click on it so that the check mark appears, and then the Menu Bar should reappear.

Firefox interface designers, please take note: As a user it is frustrating to be playing with settings and suddenly find that you're unable to put things back the way they were. Solving this problem requires the user to, a) know the term "menu bar" (many do not) in order to search it in the Help area, and b) locate the Help without having the Menu Bar, which wasn't easy.

I hope this helps someone.

Please note that this thread is about Firefox on a mobile device and not on a desktop computer.
You can see that in the Question Details at the right of the first post.

I am running Android 4.0.3 on a Toshiba AT 300. I cannot find a down arrow triangle at the top of the Firefox window. I see the refresh symbol, the bookmark star, and the 3 dot symbol. I need the menu bar active. so I can c see my bookmarks.

Hi retired_poppi, to access bookmarks in Firefox for Android, tap the address bar. Three small tabs should appear below it, one of which is Bookmarks. If you wanted a separate bookmarks button, I think you would need an add-on for that (but I don't know whether one exists).