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CSS Selector

CSS selectors are used to select the content you want to style. Selectors are the part of CSS rule set.

CSS selectors select HTML elements according to its id, class, type, attribute etc.

CSS Selectors​

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

We can divide CSS selectors into five categories:

  1. CSS Element Selector
  2. CSS Id Selector
  3. CSS Class Selector
  4. CSS Universal Selector
  5. CSS Group Selector

This page will explain the most basic CSS selectors.

1. The CSS element Selector​

The element selector selects HTML elements based on the element name.

Example: all <p> elements on the page will be center-aligned, with a red text color:

<!DOCTYPE html>
<html>
    <head>
        <style>
            p {  
                text-align:  center;  
                color:  red;  
            }
        </style>
    </head>
    <body>
        <p>This is a paragraph</p>
        <p id="elem1">Me too!</p>
        <p>And me too!</p>
    </body>
</html>

Output:

Element Selector Example

2. 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!

To select an element with a specific id, write a hash (#) character, followed by the id of the element.

Example: the CSS rule below will be applied to the HTML element with id="elem1":

<!DOCTYPE html>
<html>
    <head>
        <style>
            #elem1 {  
                text-align:  center;  
                color:  red;  
            }
        </style>
    </head>
    <body>
        <p>This is a paragraph</p>
        <p id="elem1">Me too!</p>
        <p>And me too!</p>
    </body>
</html>

Output:

Id Selector Example

note

An id name can't start with a number!

3. 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.

note

A class name should not be started with a number.

Example:

<!DOCTYPE html>  
<html>  
    <head>  
        <style>  
            .center {  
                text-align: center;  
                color: red;  
            }  
        </style>  
    </head>  
    <body>  
        <h1 class="center">This heading is red and center-aligned.</h1>  
        <p class="center">This paragraph is red and center-aligned.</p>   
    </body>  
</html>

Output:

Class Selector Example

If you want to specify that only one specific HTML element should be affected then you should use the element name with class selector.

<!DOCTYPE html>  
<html>  
    <head>  
        <style>  
            p.center {  
                text-align: center;  
                color: red;  
            }  
        </style>  
    </head>  
    <body>  
        <h1 class="center">This heading is not affected</h1>  
        <p class="center">This paragraph is blue and center-aligned.</p>   
    </body>  
</html>

Output:

Class Selector Example

4. The CSS Universal Selector​

The universal selector is used as a wildcard character. It selects all the elements on the pages.

<!DOCTYPE html>  
<html>  
    <head>  
        <style>  
            * {  
               color: green;  
               font-size: 20px;  
            }   
        </style>  
    </head>  
    <body>  
        <h2>This is heading</h2>  
        <p>This style will be applied on every paragraph.</p>  
        <p id="para1">Me too!</p>  
        <p>And me!</p>  
    </body>  
</html>

Output:

Universal Selector Example

5. The CSS Grouping Selector​

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

Let's see the CSS code without group selector.

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

As you can see, you need to define CSS properties for all the elements. It can be grouped in following ways:

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

Let's see the full example of CSS group selector:

<!DOCTYPE html>  
<html>  
    <head>  
        <style>  
            h1, h2, p {  
                text-align: center;  
                color: red;  
            }  
        </style>  
    </head>  
    <body>  
        <h1>Hello World!</h1>  
        <h2>Hello World! (Smaller)</h2>  
        <p>This is a paragraph.</p>  
    </body>  
</html>

Output:

Group Selector Example

All CSS Simple Selectors​

SelectorExampleExample description
#id#firstnameSelects the element with id="firstname"
.class.introSelects all elements with class="intro"
element.classp.introSelects only <p> elements with class="intro"
**Selects all elements
elementpSelects all <p> elements
element,element,..div, pSelects all <div> elements and all <p> elements

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