overImage="image_path"

Optional. Adobe Dreamweaver ignores the overImage attribute for items other than buttons, check buttons, radio buttons, menu buttons, color pickers, and combo buttons. This attribute specifies the path, relative to the Configuration folder, of the icon file that Adobe Dreamweaver displays when the user moves the mouse over the button. If you do not specify the overImage attribute, the button does not change when the user moves the mouse over it, except for a ring that Adobe Dreamweaver draws around the button.

Example

overImage="Toolbars/images/MM/codenav_ovr.gif"