An in-depth analysis of the concepts and principles of absolute positioning-CSS Tutorial-php.cn

An in-depth analysis of the concepts and principles of absolute positioning

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Release： 2024-01-23 09:19:05

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An in-depth analysis of the concepts and principles of absolute positioning

Absolute positioning: a CSS property that accurately controls the position of elements

Introduction:
In web design, it is very important to precisely control the position of elements. And absolute positioning is a very convenient way to achieve this goal in CSS. Absolute positioning allows us to remove elements from the normal document flow and place them in a custom position. This article will deeply analyze the concepts and principles of absolute positioning, and give specific code examples to help readers better understand this technology.

1. Concept
Absolute positioning is a common positioning method in CSS. It can detach elements from the document flow and place them according to the specified position. By using the top, right, bottom, and left attributes, we can precisely specify the position of an element relative to its nearest parent element that has a positioning attribute.

2. Principle

Out of document flow
The first feature of absolute positioning is to remove elements from the normal document flow. This means that the positioned element has no effect on other elements, and other elements have no effect on the positioned element. This gives us greater flexibility when designing web page layouts.
Positioning based on parent element
Absolutely positioned elements are positioned relative to their nearest parent element with positioning attributes. If no parent element with a positioned attribute is found, an absolutely positioned element is positioned relative to the entire document.
top, right, bottom and left attributes
top, right, bottom and left are the four most important attributes in absolute positioning. They are used to specify the offset value of an element relative to its parent element. For example, we can use top: 10px to offset the element by 10 pixels relative to the top of the parent element.

3. Code Example
The following is a simple code example that demonstrates how to use absolute positioning to precisely control the position of an element:

<!DOCTYPE html>
<html>
<head>
<style>
.container {
  position: relative;
  width: 200px;
  height: 200px;
  border: 1px solid black;
}

.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 code, We create a div container called container and set its position property to relative so that it becomes the parent element of the box. Next, we create a div element named box and set its position attribute to absolute, top attribute to 50px, and left attribute to 50px so that it will be placed at the specified position relative to the container element.

Summary:
Absolute positioning is a method in CSS that can accurately control the position of elements. By breaking away from document flow and positioning based on the parent element, we can use the top, right, bottom, and left attributes to determine the position of the element. This article gives a specific code example to help readers better understand how absolute positioning works and how to use it. Through the flexible use of absolute positioning, we can design a more beautiful and personalized web page layout.

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