Lesson 4 is devoted to the perennially-controversial topic of frames. Frames are controversial because it's easy to screw them up, with the result that many people agree with usability guru Jakob Nielsen when he says that frames suck.
I happen to disagree with Mr. Nielsen on this score, because I think that frames can be used with elegance. What's important is the skill and taste of the web designer, not the technology per se.
As noted in Lesson 2.08, there's one extremely good reason to use frames: they're much simpler than using the TABLE element and therefore enable you to focus on publishing, not coding. An added benefit is that, because they're simpler, they're also faster to download. Finally, if you'll be coding a lot of links to page fragments (see Lesson 1.11), as I did for all the cross-linking in The Ism Book, you'll want to avoid tables, since most browsers can't follow links to fragments within a table.
But I'm not here to sell you on one technology or another, just to show you how to create elegant HTML. I think you can do so with frames, so enough preamble — let's Get Framed!.