PDF (adobe.com)

About frames

A web page designed with frames displays different content in different regions of a web browser. This design is typically used to display content that doesn’t change, such as a navigation bar, in one area and content that changes in the main content area.

For example, a web page might have one narrow frame on the left side that contains navigation links, one frame along the top that contains the logo and title of the website, and one large frame that takes up the rest of the page and displays the main content.

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A.
Navigation frame

B.
Title and logo frame

C.
Main content frame.