This chapter explores HTML only as it relates to CSS. It contains design patterns that are essential for styling a document with CSS. It explores HTML at a high level with an eye toward explaining how elements can be put to use structurally and semantically. Each design pattern in this book is created using structural and semantic elements combined with CSS. There are four major types of elements used in design patterns: structural block, terminal block, multi-purpose block, and inline elements. Understanding these types of elements is key to understanding the design patterns in this book and essential to creating your own.