status: #doc 
Tags: #html #css
links: [[html-css]]
Date: 2023-08-01
___
# css selector

CSS selectors are used to "find" (or select) the HTML elements you want to style.

We can divide CSS selectors into five categories:

- Simple selectors (select elements based on name, id, class)
- [Combinator selectors](https://www.w3schools.com/css/css_combinators.asp) (select elements based on a specific relationship between them)
- [Pseudo-class selectors](https://www.w3schools.com/css/css_pseudo_classes.asp) (select elements based on a certain state)
- [Pseudo-elements selectors](https://www.w3schools.com/css/css_pseudo_elements.asp) (select and style a part of an element)
- [Attribute selectors](https://www.w3schools.com/css/css_attribute_selectors.asp) (select elements based on an attribute or attribute value)

This page will explain the most basic CSS selectors.

---

## The CSS element Selector

The element selector selects HTML elements based on the element name.
Here, all `<p>` elements on the page will be center-aligned, with a red text color: 
```css
p {  text-align: center;  
  color: red;}
  ```


---

## The CSS id Selector

The id selector uses the id attribute of an HTML element to select a specific element.
The id of an element is unique within a page, so the id selector is used to select one unique element!

```css
#para1 {  text-align: center;  
  color: red;}
```

**Note:** An id name cannot start with a number!

---

## The CSS class Selector

The class selector selects HTML elements with a specific class attribute.
To select elements with a specific class, write a period (.) character, followed by the class name.

In this example all HTML elements with class="center" will be red and center-aligned: 
```css
.center {  text-align: center;  
  color: red;}

```

You can also specify that only specific HTML elements should be affected by a class.

```css
p.center {  text-align: center;  
  color: red;}
```

HTML elements can also refer to more than one class.

In this example the `<p>` element will be styled according to class="center" and to class="large": 
```css
<p class="center large">This paragraph refers to two classes.</p>
```

**Note:** A class name cannot start with a number!

---

## The CSS Universal Selector

The universal selector `(*)` selects all HTML elements on the page.

The CSS rule below will affect every HTML element on the page: 
```css
 * {  text-align: center;  
  color: blue;}
```


---

## The CSS Grouping Selector

The grouping selector selects all the HTML elements with the same style definitions.

the h1, h2, and p elements have the same style definitions:
``` css

h1 {  text-align: center;  
  color: red;}  
  
h2 {  text-align: center;  
  color: red;}  
  
p {  text-align: center;  
  color: red;}
```

we have grouped the selectors from the code above: 

```css
h1, h2, p {  text-align: center;  
  color: red;}
```












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# References

https://www.w3schools.com/css/css_selectors.asp