Web Front-end
CSS Tutorial
What are id and Class selectors in CSS? Usage of id and Class selectors (examples)
What are id and Class selectors in CSS? Usage of id and Class selectors (examples)
This chapter will introduce to youWhat are id and Class selectors in CSS? Usage of id and Class selectors (example). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
1. id selector
The id selector can specify a specific style for HTML elements marked with a specific id.
The HTML element uses the id attribute to set the id selector, and the id selector in CSS is defined with "#".
The following style rules apply to the element attributes id="demo", id="para1":
#demo{ width: 500px; height: 200px; margin: 50px auto; }
#para1 { text-align:center; color:red; }Note: Do not start the ID attribute with a number. IDs starting with numbers are in Mozilla/Firefox Doesn't work in browser.
Sample code:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>id 选择器</title>
<style>
#demo{ width: 500px; height: 200px; margin: 50px auto; }
#para1 { text-align:center; color:red; }
</style>
</head>
<body>
<div id="demo">
<p id="para1">Hello World!</p>
<p>这个段落不受该样式的影响。</p>
</div>
</body>
</html>Rendering:
##2. Class selector
The class selector is used to describe the style of a group of elements. The class selector is different from the id selector. Class can be used in multiple elements. The class selector is represented by the class attribute in HTML. In CSS, the class selector is displayed with a dot ".": In the following example, all objects with the center class HTML elements are all centered..center {text-align:center;}<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>class 选择器/title>
<style>
.center
{
text-align:center;
}
</style>
</head>
<body>
<h1 id="标题居中">标题居中</h1>
<p class="center">段落居中。</p>
</body>
</html>
p.center {text-align:center;}Note: The first character of the class name Numbers cannot be used! It won't work in Mozilla or Firefox.
Code example:<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>css教程</title>
<style>
p.center
{
text-align:center;
}
</style>
</head>
<body>
<h1 id="这个标题不受影响">这个标题不受影响</h1>
<p class="center">这个段落居中对齐。</p>
</body>
</html>
The above is the detailed content of What are id and Class selectors in CSS? Usage of id and Class selectors (examples). 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
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
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
1387
52
How to use bootstrap in vue
Apr 07, 2025 pm 11:33 PM
Using Bootstrap in Vue.js is divided into five steps: Install Bootstrap. Import Bootstrap in main.js. Use the Bootstrap component directly in the template. Optional: Custom style. Optional: Use plug-ins.
The Roles of HTML, CSS, and JavaScript: Core Responsibilities
Apr 08, 2025 pm 07:05 PM
HTML defines the web structure, CSS is responsible for style and layout, and JavaScript gives dynamic interaction. The three perform their duties in web development and jointly build a colorful website.
How to write split lines on bootstrap
Apr 07, 2025 pm 03:12 PM
There are two ways to create a Bootstrap split line: using the tag, which creates a horizontal split line. Use the CSS border property to create custom style split lines.
Understanding HTML, CSS, and JavaScript: A Beginner's Guide
Apr 12, 2025 am 12:02 AM
WebdevelopmentreliesonHTML,CSS,andJavaScript:1)HTMLstructurescontent,2)CSSstylesit,and3)JavaScriptaddsinteractivity,formingthebasisofmodernwebexperiences.
How to resize bootstrap
Apr 07, 2025 pm 03:18 PM
To adjust the size of elements in Bootstrap, you can use the dimension class, which includes: adjusting width: .col-, .w-, .mw-adjust height: .h-, .min-h-, .max-h-
How to use bootstrap button
Apr 07, 2025 pm 03:09 PM
How to use the Bootstrap button? Introduce Bootstrap CSS to create button elements and add Bootstrap button class to add button text
How to set up the framework for bootstrap
Apr 07, 2025 pm 03:27 PM
To set up the Bootstrap framework, you need to follow these steps: 1. Reference the Bootstrap file via CDN; 2. Download and host the file on your own server; 3. Include the Bootstrap file in HTML; 4. Compile Sass/Less as needed; 5. Import a custom file (optional). Once setup is complete, you can use Bootstrap's grid systems, components, and styles to create responsive websites and applications.
How to insert pictures on bootstrap
Apr 07, 2025 pm 03:30 PM
There are several ways to insert images in Bootstrap: insert images directly, using the HTML img tag. With the Bootstrap image component, you can provide responsive images and more styles. Set the image size, use the img-fluid class to make the image adaptable. Set the border, using the img-bordered class. Set the rounded corners and use the img-rounded class. Set the shadow, use the shadow class. Resize and position the image, using CSS style. Using the background image, use the background-image CSS property.
