A
nested page template is a page template that is based on an existing page
template (also known as the root template). Nested page templates give you
more flexibility in Web sites that have both static pages and dynamic pages.
When a large Web site has several categorized pages and multiple templates
are used to manage them, it can be difficult to manage common areas and content
areas in the templates. Nested page templates help you manage common content
when a Web site has both static pages (HTML) and dynamic pages (JSP).
In the example shown
below, the Web site has one root template with multiple nested templates that
are used to create instance pages. The contents of the root template are shared
by all the nested templates and instance pages. For example, you can create
an HTML page template as the root template, and then create a nested JSP page
template for the JSP pages in your Web site, and create another nested HTML
page template for the HTML pages in your Web site.

You may have a root template that puts a company logo at the top, has an
area on the left for navigation, an area at the bottom for contact links,
and a main content area on the right. Then you could have nested templates
for different sections of your Web site (e.g., Products, About Us, Careers.).
Each nested template can be based on the root template, and define slightly
different looks, and different content, but will still have the same company
logo, a navigation area on the left, and contact links at the bottom.
A nested page template can have content areas inside the content area
of the root template. These nested page template content areas are later filled
in by the pages that are based on the nested page template. When a page is
based on the nested template, all areas of the page are read-only except for
the nested template content areas.