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Understand and use the basic properties and usage of absolutely positioned elements

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Release： 2024-01-23 09:18:15

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Understand and use the basic properties and usage of absolutely positioned elements

To master the basic properties and usage of absolutely positioned elements, specific code examples are required

In web design and development, absolute positioning is a common and commonly used layout method. . With absolute positioning, we can place an element exactly at a specified location without being affected by other elements. Mastering the basic properties and usage of absolutely positioned elements can help us better control and layout web pages. This article will introduce the basic properties and usage of absolutely positioned elements, and give specific code examples.

In CSS, the positioning method of an element is specified by using the position attribute. Absolute positioning is one of the methods, which is achieved by setting the position attribute value to absolute. Absolutely positioned elements are taken out of the document flow and positioned relative to their nearest positioned parent element. If there is no positioned parent element, the element will be positioned relative to the body element.

Absolutely positioned elements have the following basic attributes:

top: Specifies the distance of the element relative to the top of the parent element.
right: Specifies the distance of the element relative to the right side of the parent element.
bottom: Specifies the distance of the element relative to the bottom of the parent element.
left: Specifies the distance of the element relative to the left side of the parent element.

By setting the values of the top, right, bottom and left attributes, we can precisely control the position of the element. These values can be specific pixel values or percentage values. Below is a simple sample code that demonstrates how to use the absolutely positioned attribute.

<!DOCTYPE html>
<html>
<head>
  <style>
    .container {
      position: relative;
      width: 300px;
      height: 200px;
    }
    
    .box {
      position: absolute;
      top: 50px;
      left: 50px;
      width: 100px;
      height: 100px;
      background-color: red;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="box"></div>
  </div>
</body>
</html>

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In the above example code, we create a container element .container and set its width and height. We then created a .box element inside the .container and positioned it as an absolutely positioned element. By setting the values of the top and left attributes, we place the .box element inside the .container element, 50 pixels from the top and left of the parent element.

In addition to the basic position attributes, absolutely positioned elements can also use the z-index attribute to control the stacking order of elements. The value of the z-index attribute can be positive, negative, or 0. The larger the z-index value of an element, the higher it will appear on the upper layer. Below is a concrete sample code that demonstrates how to use the z-index attribute:

<!DOCTYPE html>
<html>
<head>
  <style>
    .box1 {
      position: absolute;
      top: 100px;
      left: 100px;
      width: 100px;
      height: 100px;
      background-color: red;
      z-index: 1;
    }
    
    .box2 {
      position: absolute;
      top: 150px;
      left: 150px;
      width: 100px;
      height: 100px;
      background-color: blue;
      z-index: 2;
    }
  </style>
</head>
<body>
  <div class="box1"></div>
  <div class="box2"></div>
</body>
</html>

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In the above sample code, we have created two box elements .box1 and .box2 with different z-index values. . Since .box2 has a larger z-index value, it will appear on top of .box1, thus covering part of .box1.

The basic properties and usage of absolutely positioned elements are as described above. By mastering these properties and usage, we can better control and layout web pages. At the same time, we can also combine other CSS properties and techniques to further expand and optimize the layout and design of web pages. Hopefully the code examples and instructions provided in this article will help readers better understand and apply absolute positioning.

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