A layout is defined in a JSP page, in which you specify where on the page to display the page's iViews. These locations are called containers.
Each of a page's iViews is assigned to one of the page's containers, and is displayed in that container at runtime. Within each container, each iView is displayed within a tray or frame. You can use the portal's default tray or create a custom tray for all the iViews in a container.
The layout tag library helps you to create custom page layouts by providing tags that enable you to:
Specify where on the page to place containers.
Define a custom iView tray. For a custom tray, tags enable you to create links for invoking standard tray functions, such as refreshing the iView or displaying help for the iView.
For a sample layout JSP page, see Sample Layout.
Note
It may be easiest to take an existing layout and modify it. The default layouts are contained in the com.sap.portal.layouts.default application.