In the physical world, atoms are the building blocks for all larger objects. Every type of atom, or element, has its own unique properties, but when bonded with other atoms, they create moleculeslarger structures with properties different from the parts.
Likewise, HTML tags are the building blocks of your Web page. Each tag, or element, has its own unique capabilities. Tags can be combined to create a Web page that is greater than the sum of its parts.
Whether a tag is by itself or nested deep within other tags, it can be treated as a discrete element on the screen and controlled by CSS.
Web designers use the concept of the box as a metaphor to describe the various things that you can do to an HTML element in a window, whether it is a single tag or several nested tags. This box has several propertiesincluding margins, borders, padding, width, and heightthat can be influenced by CSS.
This chapter shows you how to control the box and its properties.