search
HomeWeb Front-endCSS TutorialHow to understand CSS positioning?

How to understand CSS positioning?

The CSS Positioning property allows you to position elements.

CSS positioning and floating

CSS provides some properties for positioning and floating. Using these properties, you can create a column layout and combine part of the layout with The other part overlaps and can also accomplish tasks that have often required the use of multiple forms over the years. (Recommended study: CSS Introduction Tutorial)

The basic idea of ​​positioning is simple. It allows you to define where the element box should appear relative to its normal position, or relative to its parent. The position of an element, another element, or even the browser window itself.

Obviously, this function is very powerful and surprising. It shouldn't be surprising to know that user agents support positioning in CSS2 much better than other aspects.

Floats, on the other hand, were first proposed in CSS1 and were based on a feature added by Netscape in the early days of the Web. Floating isn't exactly positioning, but it's certainly not a normal flow layout either. We will clarify the meaning of float in a later chapter.

Everything is a box

A div, h1 or p element is often called a block-level element. This means that these elements appear as a block of content, a "block box". In contrast, elements such as span and strong are called "inline elements" because their content appears within a line, an "inline box."

You can change the type of generated box using the display property. This means that you can make inline elements (such as elements) behave like block-level elements by setting the display property to block.

You can also set display to none so that the generated element has no frame at all. This way, the box and all its contents are no longer visible and take up no space in the document.

But in one case, block-level elements are created even without explicit definition. This happens when you add some text to the beginning of a block-level element (such as a div). Even if the text is not defined as a paragraph, it will be treated as one:

<div>
some text
<p>Some more text.</p>
</div>

In this case, the box is called an unnamed block box because it is not associated with a specifically defined element.

A similar situation occurs with text lines of block-level elements. Suppose you have a paragraph containing three lines of text. Each line of text forms an unnamed box. You cannot directly apply styles to nameless blocks or line boxes because there is no place to apply styles (note that line boxes and inline boxes are two different concepts). However, it helps to understand that everything you see on the screen forms some kind of box.

CSS positioning mechanism

CSS has three basic positioning mechanisms: normal flow, floating and absolute positioning.

All boxes are positioned in the normal flow unless specifically specified. That is, the position of an element in the normal flow is determined by the element's position in (X)HTML.

Block-level boxes are arranged one after another from top to bottom, and the vertical distance between boxes is calculated from the vertical margin of the box.

Inline boxes are arranged horizontally in a row. Their spacing can be adjusted using horizontal padding, borders, and margins. However, vertical padding, borders, and margins do not affect the height of the inline box. The horizontal box formed by a line is called a line box. The height of a line box is always high enough to accommodate all the inline boxes it contains. However, setting the row height can increase the height of this box.

The above is the detailed content of How to understand CSS positioning?. For more information, please follow other related articles on the PHP Chinese website!

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
The Lost CSS Tricks of Cohost.orgThe Lost CSS Tricks of Cohost.orgApr 25, 2025 am 09:51 AM

In this post, Blackle Mori shows you a few of the hacks found while trying to push the limits of Cohost’s HTML support. Use these if you dare, lest you too get labelled a CSS criminal.

Next Level CSS Styling for CursorsNext Level CSS Styling for CursorsApr 23, 2025 am 11:04 AM

Custom cursors with CSS are great, but we can take things to the next level with JavaScript. Using JavaScript, we can transition between cursor states, place dynamic text within the cursor, apply complex animations, and apply filters.

Worlds Collide: Keyframe Collision Detection Using Style QueriesWorlds Collide: Keyframe Collision Detection Using Style QueriesApr 23, 2025 am 10:42 AM

Interactive CSS animations with elements ricocheting off each other seem more plausible in 2025. While it’s unnecessary to implement Pong in CSS, the increasing flexibility and power of CSS reinforce Lee's suspicion that one day it will be a

Using CSS backdrop-filter for UI EffectsUsing CSS backdrop-filter for UI EffectsApr 23, 2025 am 10:20 AM

Tips and tricks on utilizing the CSS backdrop-filter property to style user interfaces. You’ll learn how to layer backdrop filters among multiple elements, and integrate them with other CSS graphical effects to create elaborate designs.

SMIL on?SMIL on?Apr 23, 2025 am 09:57 AM

Well, it turns out that SVG's built-in animation features were never deprecated as planned. Sure, CSS and JavaScript are more than capable of carrying the load, but it's good to know that SMIL is not dead in the water as previously

'Pretty' is in the eye of the beholder'Pretty' is in the eye of the beholderApr 23, 2025 am 09:40 AM

Yay, let's jump for text-wrap: pretty landing in Safari Technology Preview! But beware that it's different from how it works in Chromium browsers.

CSS-Tricks Chronicles XLIIICSS-Tricks Chronicles XLIIIApr 23, 2025 am 09:35 AM

This CSS-Tricks update highlights significant progress in the Almanac, recent podcast appearances, a new CSS counters guide, and the addition of several new authors contributing valuable content.

Tailwind's @apply Feature is Better Than it SoundsTailwind's @apply Feature is Better Than it SoundsApr 23, 2025 am 09:23 AM

Most of the time, people showcase Tailwind's @apply feature with one of Tailwind's single-property utilities (which changes a single CSS declaration). When showcased this way, @apply doesn't sound promising at all. So obvio

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)