Each behaviour in the Add Behaviours menu has a dialogue box that enables you to specify the actions that should take place when a certain trigger is encountered. A trigger is an action that a visitor to your Web site may perform, such as clicking on a link, entering data into a form or mousing over a particular location on the page.
You'll find the Validate Form behaviour useful if you collect typed information from your visitors. The Validate Form behaviour can used to verify that data entered by a visitor is in the correct format or contains only valid data. Once you have configured the behaviour appropriately, select OK.
You may also change a behaviour you have added to Dreamweaver 8. To modify an existing behaviour, find the behaviour you want to edit in Code View. Select it and it will appear in the list below the Add Behaviours button in the Behaviours panel. From this point, you may modify the order in which events occur, change the event that triggers an action or delete the behaviour altogether.