But there are many generations of cruft. Table-based layouts is just one thing, how about font-tags, quirks-mode-triggering doctypes, frames, float-based layout

But there are many generations of cruft. Table-based layouts is just one thing, how about font-tags, quirks-mode-triggering doctypes, frames, float-based layouts, <!--[if IE]> and so on. Each of these might by necessary to understand in some very specific cases of legacy code. I'm just saying: Don't put this up front in a tutorial. Don't explain GOTO before explaining if-else blocks.