Even though framed sites are not a sought-after concern these days, as you can tell from this chapter, it's important to understand them because they work in a very different way from regular HTML.
You might not choose to use frames for a site, but it's a good idea to practice their use and get a feel for how they can be put to good use.
You never knowit might be just the solution you find yourself looking for one day.
And, of course, iframes have a lot of very useful applications and are commonly used in contemporary design. It is important to understand the differences between frames and iframes, and to get comfortable with both approaches.
Finally, CSS can be used to not just style the information within framed sites or with iframes, but to actually create similar effects that frames do. You'll learn more about this in upcoming chapters.
And speaking of CSS, now that you've gotten through a lot of markup, it's time to move on to learning about CSS, and how it can take all the structural elements you've been working with and add lots of attractive, useful effects.