A navigation menu, something unmissable in all websites, one of the most important factor besides content. You can have a simple navigation or a very intricate one, design and code wise. Once I learned some key navigation techniques I went on to learn how to work around WordPress generated navigation to still be able to use dropdown menus without extra plug-ins. In most cases I rather hardcode the navigation, especially if they require more specific HTML code.
Now that CSS has become mainstream a lot of tutorial focus more on advanced techniques assuming you already know the basics. Same thing goes for books, I’m a book person and I have some of the latest CSS books and more and more writers start their introduction saying that they assume you have basic and working knowledge about CSS.
Not everyone can learn and understand coding right away, myself I am good at CSS and XHTML but with PHP it took some long hours and it still does. My skills becomes rusty very fast if I don’t code regularly. This is where old tutorials come in handy, they might date back a few years but for getting back to basics or if you just started out they are the best tutorials. Most of them have a lot of user comments full of tips, adjustments and bug fixes, so plenty of resources.