Absolute positioning of CSS_html/css_WEB-ITnose
Absolute positioning of CSS:
1. Basic concept:
If relative positioning does not break away from the document flow and offset relative to the object itself is a bit confusing, then absolute positioning is definitely It cuts the knot quickly, because absolute positioning can make an object break away from the normal document flow, as if it is floating above the normal document flow, and position it relative to the element containing the object. Of course, this positioning relative to the element also varies in different situations. different.
2. How to set an element to absolute positioning:
Add the following attributes to the object to set the object to absolute positioning:
position:absolute; 或者 position:fixed
3. Positioning reference object:
You can use the top attribute and left attribute to set the offset of the absolutely positioned object.
Although absolute positioning is separated from the document flow, it also requires a reference object for positioning, but the reference object is different in different situations.
1. If the top or left attribute value is not set, then the positioning reference object of the corresponding orientation is the first-level parent element of this object. The code example is as follows:
<!DOCTYPE html> <html> <head> <meta charset=" utf-8"> <meta name="author" content="http://www.softwhy.com/" /> <title>CSS的绝对定位-蚂蚁部落</title> <style type="text/css"> body { margin:20px; } #grandfather { width:330px; height:300px; background-color:#F90; } #father { width:200px; height:200px; background-color:green; margin-left:50px; } #children { width:100px; height:100px; background-color:red; float:right; } #inner { width:50px; height:50px; background-color:blue; position:absolute; top:10px; } </style> </head> <body> <div id="grandfather"> <div id="father"> <div id="children"> <div id="inner"></div> </div> </div> </div> </body> </html>
In the above code, since the inner element uses absolute positioning and the left attribute value is not set, the positioning reference object in the horizontal direction is the first-level parent element children of the inner element. Of course, if the top attribute value is not set, the vertical positioning reference object is also children.
2. If the left or top attribute value is set:
1). If the ancestor element uses positioning, then the positioning reference object of the corresponding direction of this object is this ancestor element. If the ancestor element does not use positioning, Positioned, then the positioning reference object in the corresponding direction is the browser client area. The code example is as follows:
Example 1:
<!DOCTYPE html> <html> <head> <meta charset=" utf-8"> <meta name="author" content="http://www.softwhy.com/" /> <title>CSS的绝对定位-蚂蚁部落</title> <style type="text/css"> body { margin:20px; } #grandfather { width:330px; height:300px; background-color:#F90; } #father { width:200px; height:200px; background-color:green; margin-left:50px; position:relative; } #children { width:100px; height:100px; background-color:red; float:right; } #inner { width:50px; height:50px; background-color:blue; position:absolute; left:10px; top:10px; } </style> </head> <body> <div id="grandfather"> <div id="father"> <div id="children"> <div id="inner"></div> </div> </div> </div> </body> </html>
The above code, the inner element uses absolute Positioning, and its ancestor element father adopts relative positioning, then its positioning reference object is father.
Example 2:
<!DOCTYPE html> <html> <head> <meta charset=" utf-8"> <meta name="author" content="http://www.softwhy.com/" /> <title>CSS的绝对定位-蚂蚁部落</title> <style type="text/css"> body { margin:20px; } #grandfather { width:330px; height:300px; background-color:#F90; } #father { width:200px; height:200px; background-color:green; margin-left:50px; } #children { width:100px; height:100px; background-color:red; float:right; } #inner { width:50px; height:50px; background-color:blue; position:absolute; top:10px; } </style> </head> <body> <div id="grandfather"> <div id="father"> <div id="children"> <div id="inner"></div> </div> </div> </div> </body> </html>
In the above code, the inner element uses absolute positioning, and its ancestor elements do not use Positioned, then the vertical positioning reference object is the window. Since the left attribute value is not set, the horizontal positioning reference object is its first-level parent element children.
4. Absolutely positioned elements break away from the document flow:
As mentioned at the beginning, absolute positioning can make an element break away from the document flow, then elements in the surrounding document flow can occupy the space when this element does not break away from the document flow. Location.
The code example is as follows:
<!DOCTYPE html> <html> <head> <meta charset=" utf-8"> <meta name="author" content="http://www.softwhy.com/" /> <title>CSS的绝对定位-蚂蚁部落</title> <style type="text/css"> div { text-align:center; line-height:100px; } .father { width:400px; height:400px; background-color:green; margin:50px; } .first { width:100px; height:100px; background-color:red; position:absolute; } .second { width:120px; height:120px; background-color:blue; } </style> </head> <body> <div class="father"> <div class="first">first</div> <div class="second">second</div> </div> </body> </html>
In the above code, since the first element is out of the document flow, the second element can Occupy the position that the original first element should have occupied.
Special note: Positioned elements are often used together with the z-index attribute. For details, please refer to the detailed usage of the z-index attribute in CSS

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The official account web page update cache, this thing is simple and simple, and it is complicated enough to drink a pot of it. You worked hard to update the official account article, but the user still opened the old version. Who can bear the taste? In this article, let’s take a look at the twists and turns behind this and how to solve this problem gracefully. After reading it, you can easily deal with various caching problems, allowing your users to always experience the freshest content. Let’s talk about the basics first. To put it bluntly, in order to improve access speed, the browser or server stores some static resources (such as pictures, CSS, JS) or page content. Next time you access it, you can directly retrieve it from the cache without having to download it again, and it is naturally fast. But this thing is also a double-edged sword. The new version is online,

The article discusses using HTML5 form validation attributes like required, pattern, min, max, and length limits to validate user input directly in the browser.

This article demonstrates efficient PNG border addition to webpages using CSS. It argues that CSS offers superior performance compared to JavaScript or libraries, detailing how to adjust border width, style, and color for subtle or prominent effect

Article discusses best practices for ensuring HTML5 cross-browser compatibility, focusing on feature detection, progressive enhancement, and testing methods.

The article discusses the HTML <datalist> element, which enhances forms by providing autocomplete suggestions, improving user experience and reducing errors.Character count: 159

The article discusses the HTML <progress> element, its purpose, styling, and differences from the <meter> element. The main focus is on using <progress> for task completion and <meter> for stati

This article explains the HTML5 <time> element for semantic date/time representation. It emphasizes the importance of the datetime attribute for machine readability (ISO 8601 format) alongside human-readable text, boosting accessibilit

The article discusses the HTML <meter> element, used for displaying scalar or fractional values within a range, and its common applications in web development. It differentiates <meter> from <progress> and ex
