The role of css3 selector

The role of CSS3 selectors and code examples

CSS (Cascading Style Sheets) is a language used to define web page styles. Through CSS3 selectors, we can Precisely select and modify specific elements on your page for more flexible style control. This article will introduce the role of CSS3 selectors and provide some specific code examples.

1. The role of CSS3 selector

1. Accurately select elements: CSS3 selector can select specific elements on the page based on the element's tag name, class name, ID and other attributes. Select. Through CSS3 selectors, we can easily modify the style of a specific element without modifying the style of the entire page.
2. Convenient nested selection: CSS3 selectors support nested selection, which means that the target element can be located through layers of selectors. This nested structure of selectors makes it easier to select a combination of elements in a complex structure.
3. More flexible pseudo-class selection: CSS3 selectors also introduce a series of new pseudo-class selectors, such as: first-child (select the first child element of an element), :last-child (Select the last child element of an element) etc. These pseudo-class selectors can not only select the element itself, but also select a specific state of the element, further increasing the flexibility of style control.

2. Code examples

The following are several commonly used CSS3 selector code examples:

1. Tag selector:

   p {
     color: red;
   }

   This code selects all

   elements and sets their text color to red.

2. Class selector:

   .highlight {
     background-color: yellow;
   }

   This code means to select all elements with the highlight class and set their background color to yellow.

3. ID selector:

   #header {
     font-size: 24px;
   }

   This code means to select the element whose ID is header and set its font size to 24 pixels.

4. Descendant selector:

   .parent-class p {
     font-weight: bold;
   }

   This code indicates that all

   elements inside the element with class parent-class are selected and their text is Bold.

5. Pseudo class selector:

   a:hover {
     color: blue;
   }

   This code means to select all elements that the mouse is hovering over the link and set their text color to blue.

Through the above code examples, we can see the flexibility and power of CSS3 selectors. Combining different selectors, we can accurately select and modify specific elements on the page to achieve rich and diverse style effects.

To sum up, CSS3 selector is a very powerful tool that can help us achieve precise control over page style. By using different selectors flexibly, we can easily select specific elements and modify their styles. Whether it is a simple tag selector or a complex pseudo-class selector, it can help us achieve a variety of style effects. Therefore, mastering and using CSS3 selectors proficiently is crucial to developing high-quality web pages.

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