After the user selects an option in the pulldown menu, the new page opens in a new window. This is useful when linking to sites not within your site when you do not want the user to leave your site. Your site will remain open in the other window so the visitor can come back to it when the are finished with the popup page. You can even control the size of the popup window, whether it has scrollbars, menubars, toolbars, etc.