


Analysis of the reasons why horizontal centering is invalid when setting margin:0 auto; in css
A common problem that many friends who are new to making web pages may encounter is that adding margin:0 auto; in CSS has no effect and cannot be centered. margin:0 auto; means: the upper and lower boundaries are 0 , the left and right sides are adaptive according to the width, which actually means horizontal centering. Here are two typical errors that cause problems that cannot be centered:
1. The width is not set
<div style="margin:0 auto;"></div>
Look at the above code, there is no DIV set at all Width, how to adapt according to the width? Issues that are easier for novices to overlook.
2. DOCTYPE is not declared
1) DOCTYPE is the abbreviation of document type, which is used in web design to indicate what version of XHTML or HTML you are using. To build a standards-compliant web page, the DOCTYPE declaration is an essential and critical component.
2) Look at the code below, does it look familiar? Like this, at the top of the document, the mess above all the code is used to declare DOCTYPE:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
3) You have three options to declare DOCTYPE
* Transitional: The requirements are very Relaxed DTD, which allows you to continue to use HTML4.01 logos (but must comply with xhtml writing), the complete code is as follows:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
* Strict (Strict): strict DTD, you cannot use any presentation layer logos and attributes, such as
, the complete code is as follows:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
* Frameset: a DTD specifically designed for frame page design. If your page contains a frame, you need to use this DTD. The complete code is as follows :
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
4) As for which one to choose, just use the transitional one.
After talking for a long time, margin:0 atuo; does not work. If it cannot be centered, check whether there is a DOCTYPE statement at the top of your document. If not, just copy and paste it and it will be fine.
Also, the actual effects of margin:0 auto; and margin-left:auto; margin-right:auto; are sometimes different. The reason may be that when the height of margin-top is set to not be 0, an error will occur. Unexpected effect.

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



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.

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.

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-

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.

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.

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.

How to use the Bootstrap button? Introduce Bootstrap CSS to create button elements and add Bootstrap button class to add button text

Answer: You can use the date picker component of Bootstrap to view dates in the page. Steps: Introduce the Bootstrap framework. Create a date selector input box in HTML. Bootstrap will automatically add styles to the selector. Use JavaScript to get the selected date.
