How to set CSS styles in HTML files

HTML is a markup language used to create web pages, while CSS (Cascading Style Sheets) is a language used to describe the appearance and style of web pages. By using HTML and CSS together we can create attractive and professional looking websites. This article will introduce how to set CSS styles in HTML files.

1. Embedded style sheet

In the head tag of an HTML document, we can use the style tag to define CSS styles. This is called an embedded style sheet because CSS styles are embedded within the HTML document. Here is a basic example:

nbsp;html>


    <title>我的网站</title>
    <style>
        body {
            background-color: #ccc;
            color: #000;
            font-family: Arial, sans-serif;
        }
        h1 {
            color: #00f;
        }
    </style>


    <h1 id="欢迎来到我的网站">欢迎来到我的网站</h1>
    <p>这是我的第一篇博客文章。</p>

In the above example, we used an embedded style sheet to define the CSS styles for the body and h1 elements. Since we want to apply these styles to the entire HTML document, we place them in the head tag. As we can see, the syntax of CSS styles is very simple. We simply specify the property name we want to change, followed by a colon, and then the property value.

2. External style sheets

Embedded style sheets are very useful, but they only work on a single HTML document. If we have multiple HTML documents and want to share CSS styles between them, we can use external style sheets. An external style sheet is a separate CSS file that contains all CSS style definitions. We can link it in HTML through the link tag, as shown below:

nbsp;html>


    <title>我的网站</title>
    <link>


    <h1 id="欢迎来到我的网站">欢迎来到我的网站</h1>
    <p>这是我的第一篇博客文章。</p>

In the above example, we use the link tag to link the style.css file to the HTML document. The CSS file should contain the same CSS code as the properties of the embedded style sheet.

3. Class selector and ID selector

CSS can also select and change the style of HTML elements through class selectors and ID selectors. Class selectors start with a period (.) and are used to select elements with specific CSS classes. Multiple classes can be defined for elements. The ID selector starts with a pound sign (#) and is used to select elements with a specific ID. Each element can only have one ID. Here is a basic example:

nbsp;html>


    <title>我的网站</title>
    <style>
        .title {
            color: #f00;
            font-size: 32px;
        }
        #intro {
            font-size: 20px;
            font-weight: bold;
        }
    </style>


    <h1 id="欢迎来到我的网站">欢迎来到我的网站</h1>
    <p>这是我的第一篇博客文章。</p>

In the above example, we have defined the style of the h1 element using the class selector (.title) and the style of the p element using the ID selector (#intro) . Note that the name of the selector must be the same as the class or id attribute in the corresponding HTML element tag.

4. Other CSS Selectors

CSS has many other selectors that can help us select and change the style of HTML elements more accurately. The following are some commonly used selectors:

• Descendant selector: used to select elements within child elements, for example, div p will select all p elements nested within div elements.
• Adjacent sibling selector: used to select adjacent sibling elements. For example, p span will select the first span element after p.
• Pseudo-class selector: used to match elements in a specific state, for example: hover selects the state when the mouse is hovering over the element.

In CSS, selectors can be combined to select elements more precisely. For example, we can use the class selector and descendant selector to select all p elements in a div:

div p {
    color: #000;
    font-size: 16px;
}

In the above example, we used the div and p selectors to select all p elements nested in a div All p elements.

Summary

Through basic CSS style settings, we can define the appearance and style of the website in the HTML document. Embedded and external style sheets, class selectors and ID selectors, and other CSS selectors all make page design more flexible and personalized. We can use them to create attractive and professional looking websites.

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