You can use the Behaviors panel to add behaviors to elements, and manage the behaviors that have been added to various elements.
Insert To add a new behavior, select an element in Design view, and then click Insert. A menu opens with all of the behaviors appropriate for that element in the schema you have specified in the Authoring tab of the Page Editor Options dialog box. Click the behavior you want and customize it in the dialog box that opens.
Tag See which element is selected.
Delete Delete the selected behavior.
Move Up and Move Down The Move Up and Move Down buttons enable you to change the order of behaviors in the list. The order in which the code is executed to perform the behaviors is determined by the order of the behaviors in the list.
Events column See the events that trigger the behaviors. The drop-down list associated with a behavior allows you to change the event that causes the behavior to display. For example, you can change onmouseover to onclick to cause the behavior to occur when the user clicks the control, rather than hovering the mouse pointer over it. The list contains all the behaviors appropriate for the selected element in the schema you have specified in the Authoring tab of the Page Editor Options dialog box.
Actions column See the behavior that corresponds with the event.