Why is CSS so difficult to understand? For someone who’s been doing web sites with tables, it’s a totally different way of thinking about how design elements relate to each other.
To get a sense of how CSS works, you’ll need to orient yourself to how stuff is normally laid out on a page; how that stuff is given size and dimensions; how it can be positioned relative to its neighbors; and, finally, how it is styled.
Throughout this section, I link to the locations in W3C specifications where concepts and terms are introduced. To reduce the chaos of a ton of links, those links will appear like this link to the concept of a value. These links will have titles identifying the section of the specification by name.
When a sentence or paragraph uses a piece of the specification as its backup material, the reference is identified in a “section”, such as §, much like how a footnote reference works.