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Inheritance (page nesting) allows you to maintain a consistent design throughout the website and manage content shared by multiple pages in a single location. The portal engine implements inheritance by nesting subpages inside the content of ancestor pages on higher levels of the content tree.
What are ancestor pages?
Ancestors include all pages under which a given page is stored, from the root of the site's content tree down to the page's direct parent.
For example, the /Company/Offices/London Office page has the following ancestors:
Note how the pages are structured in the content tree: the root (master page) is the parent of the Home page, which is loaded inside the master page. You can perform nesting recursively at any level of the content tree. A necessary component for page nesting is the Page placeholder web part. This web part must be placed on the master page, and specifies where the system inserts the underlying pages. The Page placeholder on the Corporate Site root loads the sub-pages between the main menu and footer.