Make sure that you do not run Firefox in full screen mode (press F11 or Fn + F11 to toggle; Mac: command+Shift+F).
If you are in full screen mode then hover the mouse to the top to make the Navigation Toolbar and Tab bar appear.
You can click the Maximize button at the top right to leave full screen mode or right click empty space on a toolbar and use "Exit Full Screen Mode" or press F11.

Press F10 or tap the Alt key to bring up the "Menu Bar" temporarily if the Menu Bar is hidden.
You can check "View > Status Bar" if you lost the Status Bar (Firefox 3 versions do not have the Add-ons bar) or look at "View > Toolbars" if other toolbar are hidden.

See also:

• https://support.mozilla.com/kb/Menu+bar+is+missing

你没有看清楚我的问题 我不是全屏模式 OK? 我是正常模式 我的问题是 右下角有个工具 可以放大或者缩小或者还原我页面的大小 我现在右下角看不到这个工具 不知道怎么调出来

Sorry, I need to use Google translate to read your posts and your problem isn't quite clear to me.

Does this help?

It is possible that the screen is too high and that the scroll bar and the find bar and add-on bar fall off at the bottom.

Use Restore (or Maximize) in the right-click context menu of the Taskbar icon to set focus to the Firefox application if you do not see the Firefox window.

• Open the system menu via Alt+Space and see if you can move and resize that window.
• You can only resize if the window is not maximized, so you may have to undo that first.

If that works then close Firefox (File > Exit/Quit) to save that setting.

See also:

• http://kb.mozillazine.org/Resizing_oversize_window

If the above didn't help then try to delete the localstore.rdf file in the profile folder.
See:

• http://kb.mozillazine.org/Corrupt_localstore.rdf