What are css style selectors

CSS style selector refers to a mechanism used in CSS to select and style corresponding elements based on their specific attributes or relationships. In the process of writing web pages, selectors are an essential part, which help us control the appearance and layout of the page display. This article will introduce some common CSS style selectors.

1. Element Selector(Element Selector)
   The element selector is one of the most common selectors. It selects elements on the page based on the element name. For example, the p selector will match all <p></p> elements in HTML and set corresponding styles for them.

p {
    color: red;
}

2. Class Selector (Class Selector)
   The class selector is prefixed with ".", which selects elements on the page by specifying the CSS class of the element. For example, you can use the class attribute in HTML to categorize elements and add the same styles to these elements. The syntax of class selector in CSS is: .classname.

.warning {
    color: yellow;
}

3. ID Selector
   The ID selector is prefixed with "#", and the element ID on each page is unique. Using the ID selector, you can select exactly the specified element. The syntax of ID selector in CSS is: #idname.

#header {
    background-color: black;
    color: white;
}

4. Descendant Selector(Descendant Selector)
   The descendant selector selects elements in child elements. In CSS, the syntax for a descendant selector is: parent child. For example, in the following example, the h1 element will only match the h1 tag inside the posterID element:

#posterID h1 {
    color: blue;
}

5. Adjacent Sibling Selector (Adjacent Sibling Selector)
   Adjacent Sibling Selector can be selected The first sibling immediately following an element. In CSS, the syntax for adjacent sibling selectors is: A B. For example, the following CSS style selects the first p element immediately following the h2 element.

h2 + p {
    color: #000000;
}

6. Attribute Selector (Attribute Selector)
   The attribute selector selects based on the attribute value of the element. For example, you can select all elements with a specified attribute value. The syntax of the attribute selector is: [attribute=value]. The following example uses an attribute selector that selects all elements that contain href attributes whose values ​​begin with "https://":

a[href^="https://"] {
    color: green;
}

7. Pseudo-class selector (Pseudo-Class Selector)
   The pseudo-class selector is a CSS selector that can select elements based on their status or position. Commonly used pseudo-class selectors include:hover, :focus and :first-child, etc. Their syntax is: :pseudo-class.

a:hover {
    background-color: yellow;
}

This article introduces the common usage of CSS style selectors. Each selector has its own specific syntax and purpose, which can be selected according to the specific situation. Using CSS style selectors can make web pages look more beautiful and improve development efficiency.

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