How to use css

CSS is a very important front-end technology that allows us to visually display web content, thereby providing our users with a beautiful, easy-to-use interactive platform. In this article, we will discuss the use of CSS in detail so that you can easily learn how to use CSS to beautify web pages.

1. Introducing CSS

First, let’s take a look at how to add CSS to an HTML web page. In order to apply CSS to your HTML files, you can use internal CSS or external CSS.

• Internal CSS: You can add CSS code by inserting atag in the head tag. For example:

     
  
欢迎来到我的网站！
  

In this example, we define the background color of the body element and the font color and font size of the p element.

• External CSS: You can also put the CSS code in an external file and reference it into the HTML page through the link tag. For example:

In a file named styles.css, we can define styles as follows:

body { background-color: #f5f5f5; } p { color: #333; font-size: 16px; }

Reference the stylesheet in HTML through the link tag:

     
  
欢迎来到我的网站！
  

2. CSS Selector

CSS selector is a notation for selecting web page elements. For example, to select all p elements and set their font color to red, you would write:

p { color: red; }

In this example, the selector is p, which means to select all p elements. You can also select elements based on class name, ID, relationship, etc. For example:

/* 选择所有具有class为"active"的元素*/ .active { color: blue; } /* 选择所有ID为"header"的元素*/ #header { background-color: pink; } /* 选择p元素的子元素中的第一个元素*/ p:first-child { font-weight: bold; }

3. Style Properties

There are many properties in CSS that can be used to define the style of an element. Some of the most commonly used properties are listed below:

• color: Text color
• background-color: Background color
• font-size: Font size
• font-family：Font
• text-align：Text alignment
• font-weight：Font bold
• border：Element border

For example, to set the background color of an element to blue, you would write:

background-color: blue;

4. CSS Box Model

The box model is a type of The way an element is laid out, consisting of its content, inner border, outer border, and padding. By default, each element is laid out according to the box model.

The components of the box model look like this:

• Content: The actual content of the element, such as text or an image
• Padding: Between the content and the border , can be set using the padding attribute
• Border: located between the inner margin and the outer margin, can be set using the border attribute
• Margin: located between the element and its surrounding elements, can be Use the margin attribute to set it

You can modify the component size of the box model in the following ways:

/* 修改内边距 */ padding-top: 10px; padding-bottom: 10px; padding-left: 20px; padding-right: 20px; /* 修改边框 */ border-width: 2px; border-color: red; /* 修改外边距 */ margin: 20px;

5. Responsive design

Finally, Let’s talk about responsive design. Responsive design is a design method that allows a website to adapt to the screen sizes of different devices to provide users with a better experience.

By using CSS media queries, we can set different styles for different screen sizes. For example:

/* 在窗口宽度小于600px时，p元素字体大小设置为14px */ @media(max-width: 600px) { p { font-size: 14px; } }

In this example, we use the @media query syntax to define a media query that will apply styles when the window width is less than 600px. This way we can optimize our website for mobile devices.

Conclusion

How to use CSS correctly is a skill that every front-end developer must master. In this article, we discussed how to introduce CSS, how to use selectors, style properties, and the CSS box model. We also explored responsive design and demonstrated how to use @media queries to target styles for different devices. Now you can start using CSS to beautify your website and enhance user experience.

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