Another form of contextual user assistance are tooltips. Tooltips are small pop-up windows that display the name of a control when the control has no text label. The most common use of tooltips is for toolbar buttons that have graphic labels, as shown in Figure 12.6, but they can be used for any control.
Figure 12.6 A tooltip for a toolbar button
Display a tooltip after the pointer, or pointing device, remains over the button for a short period of time. The tooltip remains displayed until the user presses the button or moves off of the control, or after another time-out. If the user moves the pointer directly to another control supporting a tooltip, ignore the time-out and display the new tooltip immediately, replacing the former one.
Note 
For more information about toolbars and tooltip controls, see Chapter 7, "Menus, Controls, and Toolbars."
If you use the standard toolbar control, the system automatically provides support for tootips. It also includes a tooltip control that can be used in other contexts. If you create your own tooltip controls, make them consistent with the system-supplied controls.