Make layers appear and disappear (see Chapter 12).
Require visitors to fill out certain fields in a form (Chapter 10). For example, when you want to make sure an email address or name is entered before the visitor submits the form.
Open a new browser window to a specified size, with or without scroll bars, status bar, location bar, and other Web browser “chrome.”
Let your visitors navigate a Web site using a pop-up menu.
Give feedback to the visitor in a dialog box or in the browser’s status ...