HTML元素大小和位置相对于谁的问题_html/css

Home

Web Front-end

HTML Tutorial

HTML元素大小和位置相对于谁的问题_html/css_WEB-ITnose

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 24, 2016 am 11:31 AM

一、如果元素的position属性值为absolute，那么此时分为两种情况：

1. 父级（包括直接父级和间接父级）元素中没有定义position属性（即默认属性static），那么该元素会参照页面，以页面为基准进行定位，top, left等属性会参照页面。

如果该元素的width和height属性是百分数的话，那么这两个属性也是参照页面的宽度和高度。

<!doctype html><html><head><meta charset="utf-8"><style>*{margin: 0; padding: 0;}#div1 {    width: 200px;    height: 200px;    background: #ccc;}#div2 {    width: 50%;    height: 50%;    background: #aaa;    top: 100px;    left: 100px;    position: absolute;}</style></head><body><div id="div1">    <div id="div2"></div></div></body></html>

以上代码中，div2是绝对定位，而其父级元素没有设置position属性，那么该元素就会以页面为参照进行定位。

从图中可以看到，div2是相对于页面定位的，而且其宽度和高度是页面宽高的一半。

从控制台可以看到，页面的宽度和高度正好是div2元素的2倍。

2. 父级元素定义了position属性(relative或absolute)，则会参照父级元素。

<!doctype html><html><head><meta charset="utf-8"><style>*{margin: 0; padding: 0;}#div1 {    width: 200px;    height: 200px;    background: #ccc;    position: relative;    top: 100px;    left: 100px;}#div2 {    width: 50%;    height: 50%;    background: #aaa;    top: 100px;    left: 100px;    position: absolute;}</style></head><body><div id="div1">    div1    <div id="div2">div2</div></div></body></html>

从图中可以看到，div2是相对于div1定位的，宽度和高度也是相对于div1

二、如果元素的position属性值为relative，那么该元素相对于其正常位置（即position:static）定位。

默认情况下宽度会占满父容器，高度根据本身内容决定。当是父元素的第一个子元素时，位置会在父元素的左上角。

那么设置其位置和大小就会以自己为参照，height的情况特殊，当设置height时，会以充满父容器的状态为参照。

<!doctype html><html><head><meta charset="utf-8"><style>*{margin: 0; padding: 0;}#div1 {    width: 100px;    height: 100px;    background: #ccc;}#div2 {    width: 50%;    height: 50%;    background: #aaa;    top: 100px;    left: 100px;    position: relative;}</style></head><body><div id="div1">    <div id="div2"></div></div></body></html>

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Difficulty in updating caching of official account web pages: How to avoid the old cache affecting the user experience after version update?Mar 04, 2025 pm 12:32 PM

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,

How do I use HTML5 form validation attributes to validate user input?Mar 17, 2025 pm 12:27 PM

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

What are the best practices for cross-browser compatibility in HTML5?Mar 17, 2025 pm 12:20 PM

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

How to efficiently add stroke effects to PNG images on web pages?Mar 04, 2025 pm 02:39 PM

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

What is the purpose of the <datalist> element?Mar 21, 2025 pm 12:33 PM

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

What is the purpose of the <progress> element?Mar 21, 2025 pm 12:34 PM

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

How do I use the HTML5 <time> element to represent dates and times semantically?Mar 12, 2025 pm 04:05 PM

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

What is the purpose of the <meter> element?Mar 21, 2025 pm 12:35 PM

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

See all articles