In addition to aiding in the presentation of information, frames make navigating an Internet site easier. Frames can contain fixed elements, such as banners or navigation bars, that remain constant onscreen. Keeping content linked to the context in which it's presented has been one of the biggest challenges facing Web-site designers. With a book, it's usually easy to figure out how each page relates to the rest of the information the volume contains. You can glance at the chapter headings, flip to the table of contents, scan through subheads, and look at how far into the book you've gotten.
Web sites are quite a different story.
You can't see their physical boundaries, and it's been difficult to track the context of the content you're viewing. Now, with frames, you're able to both view the content and keep in mind the context in which it appears. The content area of some pages is segmented into rectangular frames, each frame containing its own page. Generally, toolbar and menu items affect the top-level page. You can select a frame by clicking inside it.