The Box Model

All HTML elements can be considered boxes. Even if you see a circle, it's living within a box.

The CSS box model describes this principal - a box wraps around all HTML elements, and it consists of: margins, borders, padding, and the actual content. This model allows us to place a border around elements and space elements in relation to other elements.

With CSS properties and values, it is possible to apply specific styles to each of these elements, and change the way they behave and/or display on the page.

The image below illustrates the box model and what you should have seen in your dev tools:

From www.theslate.org

But what do these different layers mean, and how are they relating to one another?

• Margin - clears an area around the border; the margin does not have a background color, it is completely transparent
  • The margin is outside the element
• Border - a border that goes around the padding and content; the border is affected by the background color of the box
  • The border is inside the element
• Padding - clears an area around the content; the space between the content and the border; the padding is affected by the background color of the box
  • The padding is inside the element
• Content - The content of the box, where text and images appear
  • The content is inside the element

Layers of the Box Model

Let's get go into some more detail and practice with each of these elements of The Box Model.

Margin

The margin is the space around the element. The larger the margin, the more space between our element and the elements around it. We can adjust the margin to move our HTML elements closer to or farther from each other.

Let's start with our margins. Adjusting our margins not only moves our element relative to other elements on the page but also relative to the "walls" of the HTML document.

For instance, if we take an HTML element with a specific width (such as our <div> in the editor) and set its margin to auto - this tells the document to automatically put equal left and right margins on our element, centering it on the page.

If you want to specify a particular margin, to a particular side, you can do it like this:

div {
  margin-top: /*some value*/;
  margin-right: /*some value*/;
  margin-bottom: /*some value*/;
  margin-left: /*some-value*/;
}

You can also set an element's margins all at once: you just start from the top margin and go around clockwise (going from top to right to bottom to left). For instance,

div {
  margin: 1px 2px 3px 4px;
}

You can do top-bottom and side side - let's add this to our css for now:

div {
  margin: 0 auto;
}

Border

The border is the edge of the element. It's what we've been making visible every time we set the border property.

Borders can be set in two ways, just like your margins and just like we've talked about previously.

div {
  border: 5px solid black;
}

/* OR */

div {
  border-width: 5px;
  border-style: solid;
  border-color: black;
}

Padding and Content

The padding is the spacing between the content and the border. We can adjust this value with CSS to move the border closer to or farther from the content.

Padding can be set in two ways, just like your margins.

div {
  padding: 2px;
}

/* OR */

div {
  padding-top: 3px;
  padding-right: 1px;
  padding-bottom: 0px;
  padding-left: 9px;
}

/* OR */

div {
  padding: 3px 1px 0 9px;
}

Padding becomes more apparent when we have "stuff" inside the box.