Setting css is invalid

In recent years, with the rapid development of Internet technology, more and more websites and applications use CSS to beautify and layout pages. However, in actual applications, we will encounter some strange problems, such as setting the css style to be invalid. What is the reason? Next, let’s analyze it.

1. Lack of imported style files or wrong reference order
During the development process, many new developers may forget to introduce style files, or there may be problems with the reference order of style files. At this time, the browser cannot recognize the style file, resulting in invalid css settings.

Solution:
1. Check whether the style file has been introduced. If not, use the tag within the tag to introduce it;
2. Check whether the reference sequence is Correct, if incorrect, quote in the correct order.

2. The style selector is used incorrectly or there is a problem with the style priority level
In CSS, different style selectors have different priorities. Among them, the id selector> class selector> tag Selector. If the same selector appears in the style sheet, the later style will overwrite the previous style, resulting in invalid CSS settings.

Solution:
1. Use a more specific selector, such as the id selector;
2. Use !important to force priority. However, using !important will affect the maintainability of the page, so use it with caution.

3. Wrong syntax appears in the style sheet
In the css style sheet, if there is wrong syntax, such as spelling errors, symbol errors, etc., it will cause the css setting to be invalid.

Solution:
1. Carefully check the grammatical issues in the css style sheet, such as whether spelling, symbols, etc. are correct;
2. You can use some css grammar detection tools to check for errors and potential question.

4. Browser compatibility issues
Different browsers parse CSS standards to different degrees, resulting in invalid CSS settings. For example, some browsers may not support newly added CSS styles, or have their own implementations of certain CSS properties.

Solution:
1. Try to use widely supported CSS syntax and attributes;
2. You can use CSS Hack to solve some browser compatibility issues.

5. The css style becomes invalid after JavaScript is used to operate DOM elements.
When JavaScript is used to operate DOM elements, the style of the element may change, resulting in invalid css settings.

Solution:
1. After JavaScript operates the DOM element, you need to check whether the css style is still in effect;
2. You can use attribute selectors and other methods to keep the style in effect.

To sum up, there may be many reasons why setting css is invalid, but as long as you analyze and investigate carefully, you can always find a solution. Therefore, we should pay attention to details during the development process and solve problems in a timely manner to achieve code optimization and improvement.

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