Selectors help you to address tags that have no ID's or classes. In the previous chapter I was talking about
those pseudo classes and elements :first-child and :first-line and :first-letter. They are selectors, too. They help you
address parts that have no ID or class, or at least you don't know which one it might be, and you don't have to know.
But these are not the only selectors, there are a lot more, for very complex tasks.
Certainly the more sophisticated selectors that are described in this chapter do not work on a certain browser.