Theory of some commonly used CSS code query tools and basic knowledge

In website development, CSS (cascading style sheets) is a very important part. It controls the style and layout of web pages, helping to improve the readability, aesthetics and user experience of the website. However, even experienced developers may encounter problems when writing CSS code. When these problems occur, they can be queried through CSS code to resolve them.

CSS Code Query is a widely used tool for querying and finding problems in CSS code. It allows developers to find bugs or solve problems easily and quickly, saving time and effort. In this article, we will introduce the basic knowledge and functions of CSS code query.

1. CSS code query tool

First, let’s take a look at commonly used CSS code query tools. The following are some commonly used tools:

1.1 W3C CSS Validator

W3C CSS Validator is a free query tool that can be used to verify whether the syntax of CSS code is correct. It uses W3C standards to determine whether a file conforms to the specification. Using the W3C CSS validator, developers can quickly detect whether there are syntax errors, tag errors, style attribute errors, etc.

1.2 CSS Lint

CSS Lint is a free online CSS code query tool that can detect potential problems in CSS. It analyzes CSS code and recommends modifications to avoid common mistakes and bad practices. In addition, CSS Lint also provides an assessment of code health, readability, and maintainability.

1.3 CSSTidy

CSSTidy is a free CSS code query tool that can format and compress CSS code. It eliminates redundant code, making it more compact and easier to read, and reduces web page load times. Using CSSTidy, developers can easily optimize CSS code to improve website performance.

1.4 CSS Prefixer

CSS Prefixer is a free tool for applying browser prefixes to CSS code. Developers can enter the required CSS properties and values, and the tool will add the appropriate browser prefixes, ensuring the website is compatible across browsers.

2. Basic knowledge of CSS code query

In addition to the above tools, CSS code query also has some basic knowledge points that developers should understand.

2.1 Selector

The selector in CSS code is used to select HTML elements and add styles to them. For example, with the selector "p", you can apply the same style to all paragraph elements.

2.2 Attributes

Attributes in CSS code are used to define the style of HTML elements. For example, the "color" attribute defines the text color, and the "background-color" attribute defines the background color of the element.

2.3 Value

The value of any CSS property is composed of one or more values that are used to define a specific style of the element. For example, the selector "p" can set the text color attribute "color" to a value of "red".

2.4 Inheritance

In CSS, styles can be inherited to their parent elements. For example, if there is a "font-size" attribute in the selector "body", then the value of that attribute will automatically be applied to all child elements.

2.5 Cascading

The cascading mechanism in CSS allows developers to control the priority of different styles within the same element. Styles with higher priority will override styles with lower priority. For example, the "id" selector will have higher priority than the "class" selector.

3. Specific examples

The following are some common examples:

3.1 Find unclosed tags

< div> This is a paragraph

3.2 Check for duplicate style attributes

p{
color: red;
color: blue;
}

3.3 Check Incorrect spelling of style attribute

p{
fon-size: 12px;
}

4. Summary

CSS code query is the web page an important part of development. It can help developers quickly solve CSS problems and optimize websites more effectively. This article introduces some commonly used CSS code query tools and basic knowledge, hoping to help readers better understand the concept and application of CSS code query.

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