What is the reason for css failure?

Causes for css failure: 1. The div tag is not closed; 2. Improper DOCTYPE declaration; 3. Ending slash; 4. Overriding the CDATA tag in JavaScript; 5. Poor nesting.

The operating environment of this tutorial: windows7 system, css3 version, DELL G3 computer.

Causes of css failure:

1. The div tag is not closed

This is the most common reason for layout design failure one. It’s always surprising when we learn how many delicate layout designs fail because of this. Open div tags are one of the most common layout design mistakes and one of the hardest to diagnose. The validator sometimes points to the wrong opening div tag, which can be like finding a needle in a haystack.

2. Improper DOCTYPE declaration

Not declaring DOCTYPE, or incorrectly declaring DOCTYPE at the beginning of the file, is also a common mistake. According to general experience, Strict DOCTYPE is the highest level of verification everyone pursues. Strict validation indicates that your web page will display optimally on all browsers.

3. Ending slash

If your website cannot be verified, it is very likely that the ending slash is missing somewhere in the code. It's easy to overlook things like trailing slashes, especially in elements like image tags.

This is not valid in a strict DOCTYPE. To solve this problem, add "/" at the end of the img tag.

4. JavaScript

If Strict DOCTYPE has been declared, you need to override the CDATA tag in JavaScript. This aspect of the verification process stumps many programmers, as websites tend to use embedded JavaScript for ads and tracking scripts.

5. Bad nesting

Nesting means elements are included within elements. It is easy for us to confuse the order of nested elements. For example, start the strong tag before the div tag, but then close the div tag first. This may not change the section layout, but it will invalidate your section design.

If you still can't find it, it is recommended to use "Developer Mode"/"Debug Mode" (open with F12) to check which attributes the corresponding element has inherited, and whether other styles have overridden the styles you set.

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