Exploring CSS box model properties: padding, margin and border

Exploration of CSS box model properties: padding, margin and border

The CSS box model is one of the important concepts in web page layout. In front-end development, understanding and correctly using padding, margin and border properties is key. This article will delve into the usage and correlation of these three properties, and provide specific code examples.

1. Introduction to the box model
The box model consists of four parts: content, padding, border and margin. Among them, the content refers to the actual content inside the element, the padding is the empty space between the content and the border, the border is the line surrounding the content and padding, and the margin is the distance between the element and other elements.

2. Padding attribute
The padding attribute is used to set the size of the inner margin of the element. You can use a single value to set the same padding in all four directions, or you can use four values ​​to set padding in the top, right, bottom, and left directions.

Code example:

.box {
  padding: 20px; /* 上下左右内边距都是 20px */
}

.box {
  padding: 10px 20px; /* 上下内边距是 10px，左右内边距是 20px */
}

.box {
  padding: 10px 20px 30px 40px; /* 上内边距是 10px，右内边距是 20px，下内边距是 30px，左内边距是 40px */
}

3. Margin attribute
The margin attribute is used to set the size of the outer margin of the element. Similar to the padding property, you can use a single value or four values ​​to set the same or different margins for the four directions.

Code example:

.box {
  margin: 20px; /* 上下左右外边距都是 20px */
}

.box {
  margin: 10px 20px; /* 上下外边距是 10px，左右外边距是 20px */
}

.box {
  margin: 10px 20px 30px 40px; /* 上外边距是 10px，右外边距是 20px，下外边距是 30px，左外边距是 40px */
}

4. border attribute
The border attribute is used to set the style, width and color of the element border. There are three sub-properties that can be set: border-width (border width), border-style (border style) and border-color (border color).

Code example:

.box {
  border-width: 1px; /* 边框宽度为 1px */
  border-style: solid; /* 实线边框 */
  border-color: #000; /* 边框颜色为黑色 */
}

.box {
  border: 2px dashed #ff0000; /* 边框宽度为 2px，虚线边框，颜色为红色 */
}

5. Calculation of width and height of box model
In the box model, the calculation of the width and height of an element includes the sum of the content, padding, and border. For example, if the width of a box is set to 100px, padding is set to 10px, and border-width is set to 1px, then the actual width of the box is 100px 10px 10px 1px 1px = 122px.

6. Association of box model attributes
There is a certain correlation between padding, margin and border attributes. When multiple adjacent elements have margins, the margins between them are combined into one larger margin. Padding and borders will not merge.

7. Summary
Through the introduction of this article, we have learned that padding, margin and border are important box model properties in CSS. Properly setting these properties can control the layout and style of elements. It should be noted that the box model attributes are related, especially the margins will be merged. In actual development, these attributes can be used flexibly as needed to achieve a satisfactory web page layout effect.

Through the above exploration of CSS box model properties, I hope readers can better understand and apply these properties and improve front-end development capabilities.

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