Chapter 7. The Box Model

In this chapter, I discuss one of the most important concepts in CSS-based web design, the box model. The box model is a set of rules that dictate how width, height, padding, borders, and margin are measured on HTML elements.

In this chapter, I discuss:

  • The CSS box model

  • CSS box model properties, padding, margins, borders, width, and height

  • Controlling line height

  • Establishing minimum and maximum dimensions

  • Overflowing content

The next section begins with an overview of what the box model is.


The CSS box model is a collection of properties that define the amount of space around an element, its dimensions, its margins, its borders, and padding between text content and the borders. In Figure 7-1, you see a diagram of the box model.

In Figure 7-1 you see what the different components that come together to make the box model look like. Around the outside of an element is space called the margin, inside of the margin is the border, inside of the border is the padding, and inside of the padding is the content of the element. Figure 7-2 takes the box model in Figure 7-1 and reproduces it in an (X)HTML document with CSS.

Figure 7-1

Figure 7-1. Figure 7-1

Figure 7-2a

Figure 7-2a. Figure 7-2a

The CSS in Figure 7-2a is combined with the markup in Figure 7-2b.

Figure 7-2b. Figure 7-2b

The result of ...

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