Where should the css file be placed?
The css file should be placed in the head at the top of the HTML. Reason: The browser parses the HTML document from top to bottom. If the CSS is placed at the bottom, the page can be rendered gradually, but after the CSS is downloaded and parsed, the text and images that have been rendered will need to be redrawn according to the new style. , which is a bad user experience.
The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.
css files should be placed in the head at the top of the HTML.
#why?
<link rel="stylesheet" href="home.css">
The href (HyperText reference) attribute in the link tag represents a hypertext reference. When CSS uses href reference, the browser will recognize it The document is CSS and is downloaded in parallel. It will not stop loading the current document. When loading HTML to generate a DOM tree, the DOM tree can be rendered at the same time. This can prevent flickers, white screens or confusing layouts.
In the most ideal situation, we hope that the browser will gradually render the downloaded CSS and gradually display the page to the user. However, in order to avoid re-rendering page elements when styles change, the browser blocks the gradual rendering of content. The browser waits for all styles to be loaded before rendering the page at once.
If the CSS file is placed at the bottom, the browser prevents the content from being rendered gradually. While the browser is waiting for the last CSS file to be downloaded, a "white screen" appears (white screen when a new connection is opened, and then Text appears first, images appear last, and styles appear last). This is very serious, because when the network speed is very slow, the CSS download time is relatively long, which naturally brings a "white screen" to the user for a long time, and the user experience is very poor.
The CSS file is placed at the top because the order of placement determines the priority of downloading, and more importantly, the rendering mechanism of the browser.
css will not affect the generation of the DOM tree during the loading process, but it will affect the generation of the Render tree, which in turn affects the layout. Therefore, generally speaking, the link tag of style needs to be placed as much as possible In the head, because the DOM tree is parsed from top to bottom, and the css style is loaded asynchronously, in this case, parsing the body node under the DOM tree and loading the css style can be as parallel as possible, speeding up the Render tree. The speed of generation.
Put the CSS at the bottom, and the page can be rendered gradually. However, after the CSS is downloaded and parsed, the text and images that have been rendered need to be redrawn according to the new style. This is a bad user experience. experience.
(Learning video sharing: css video tutorial)
The above is the detailed content of Where should the css file be placed?. For more information, please follow other related articles on the PHP Chinese website!

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 article discusses useEffect in React, a hook for managing side effects like data fetching and DOM manipulation in functional components. It explains usage, common side effects, and cleanup to prevent issues like memory leaks.

Lazy loading delays loading of content until needed, improving web performance and user experience by reducing initial load times and server load.

Higher-order functions in JavaScript enhance code conciseness, reusability, modularity, and performance through abstraction, common patterns, and optimization techniques.

The article discusses currying in JavaScript, a technique transforming multi-argument functions into single-argument function sequences. It explores currying's implementation, benefits like partial application, and practical uses, enhancing code read

The article explains React's reconciliation algorithm, which efficiently updates the DOM by comparing Virtual DOM trees. It discusses performance benefits, optimization techniques, and impacts on user experience.Character count: 159

The article explains useContext in React, which simplifies state management by avoiding prop drilling. It discusses benefits like centralized state and performance improvements through reduced re-renders.

Article discusses preventing default behavior in event handlers using preventDefault() method, its benefits like enhanced user experience, and potential issues like accessibility concerns.

The article discusses the advantages and disadvantages of controlled and uncontrolled components in React, focusing on aspects like predictability, performance, and use cases. It advises on factors to consider when choosing between them.
