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Learn to Code HTML and CSS: Opening the Box Model

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In this chapter from Learn to Code HTML and CSS: Develop and Style Websites, Shay Howe discusses the box model and how it works with HTML and CSS, and also looks at a few new CSS properties.
This chapter is from the book

We’ve familiarized ourselves with HTML and CSS; we know what they look like and how to accomplish some of the basics. Now we’re going to go a bit deeper and look at exactly how elements are displayed on a page and how they are sized.

In the process we’ll discuss what is known as the box model and how it works with HTML and CSS. We’re also going to look at a few new CSS properties and use some of the length values we covered in Lesson 3. Let’s begin.

How Are Elements Displayed?

Before jumping into the box model, it helps to understand how elements are displayed. In Lesson 2 we covered the difference between block-level and inline-level elements. To quickly recap, block-level elements occupy any available width, regardless of their content, and begin on a new line. Inline-level elements occupy only the width their content requires and line up on the same line, one after the other. Block-level elements are generally used for larger pieces of content, such as headings and structural elements. Inline-level elements are generally used for smaller pieces of content, such as a few words selected to be bold or italicized.


Exactly how elements are displayed—as block-level elements, inline elements, or something else—is determined by the display property. Every element has a default display property value; however, as with all other property values, that value may be overwritten. There are quite a few values for the display property, but the most common are block, inline, inline-block, and none.

We can change an element’s display property value by selecting that element within CSS and declaring a new display property value. A value of block will make that element a block-level element.

1.   p {
2.     display: block;
3.   }

A value of inline will make that element an inline-level element.

1.   p {
2.     display: inline;
3.   }

Things get interesting with the inline-block value. Using this value will allow an element to behave as a block-level element, accepting all box model properties (which we’ll cover soon). However, the element will be displayed in line with other elements, and it will not begin on a new line by default.

1.   p {
2.     display: inline-block;
3.   }
Figure 4.1

Figure 4.1 Three paragraphs displayed as inline-block elements, sitting one right next to the other in a horizontal line

Lastly, using a value of none will completely hide an element and render the page as if that element doesn’t exist. Any elements nested within this element will also be hidden.

1.   div {
2.     display: none;
3.   }

Knowing how elements are displayed and how to change their display is fairly important, as the display of an element has implications on how the box model is rendered. As we discuss the box model, we’ll be sure to look at these different implications and how they can affect the presentation of an element.

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