The Option Inspector
Many aspects of the Mathematica front end, such as the styles of cells, the appearance of notebooks, or the parameters used in typesetting, are controlled by options. For example, text attributes such as size, font, and color each correspond to a separate option. You can set options by directly editing the expression for a cell or notebook. But in most cases it is simpler to use the Option Inspector.
The Option Inspector is a special tool for viewing and modifying option settings. It provides a comprehensive listing of all front end options, grouped according to their function. You can specify not only the setting for an option, but also the level at which it will take effect, i.e. globally, for an entire notebook, or for a selection.
To use the Option Inspector, click Format Option Inspector.... This brings up a dialog box with two pop-up menus on top. The pop-up menu on the right allows you to choose if you want the options listed by category, alphabetically, or as text. The pop-up menu on the left specifies the level at which options will take effect.