Missing toolbar and buttons
If your toolbar is missing in the Finder, Apple Mail, and some other programs, it is likely you have just hidden it - even if you don't realize you did.
These programs feature a small oval button that lets you collapse and expand their toolbars, to hide the buttons that would normally appear. In the Finder, the hidden toolbar might make the window appearance change from brushed metal to a brighter, less adorned look. In Mail, you would lose buttons like "Get Mail" and "Delete." While those functions should still be available in the program's menus, it can be more convenient to have them in the toolbar so that you can click on buttons.
This oval widget appears in the top right corner of the window's title bar (the section of the window that shows its name), and resembles a Tic-Tac® breath mint. We have noted it in the Finder and Apple Mail, but it can appear in virtually any Mac OS X program that has toolbars.
Clicking on this title bar button when the toolbar is visible will hide the toolbar, allowing you to have a larger main window and see more files, mail messages or other content appropriate to the application. When the toolbar is not visible, clicking the widget will expand the toolbar so you can see it and its buttons again.
In most applications, you should also be able to toggle the state of the toolbar - visible or hidden - from the View menu. Choose "Hide Toolbar" if the toolbar is visible, or "Show Toolbar" if it is not.
It is easy enough to click on this collapse/expand button by accident or error, since it is in the same location used by a window control in classic Mac OS as well as Microsoft Windows.