CSS Selectors

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

CSS selectors are five categories

  • Simple selectors 
  • Combinator selectors 
  • Pseudo-class selectors
  • Pseudo-elements selectors
  • Attribute selectors

Simple selectors

  • The simple selectors select elements based on name, id, class.

Name simple selector

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

id Selector

  • The id of an element is unique within a page, so the id selector is used to select one unique element.
  • Id selector call the id by hash (#)

Note: An id name cannot start with a number!

Example
<!DOCTYPE html>
<html>
<head>
<title></title>
<style>
#p {
text-align: center;
background-color: seagreen;
color: white;
font-size: 20px;
}
</style>
</head>
<body>
<h1>This is first heading</h1>
<p id="p">This is paragraph</p>
<h3>This is third heading</h3>
<h2>This is second heading</h2>
<p id="p">This is paragraph</p>
</body>
</html>

CSS class Selector

  • The class selector selects HTML elements with a specific class attribute. 
  • Class selector call the id by Dot (.)

Note: An id name cannot start with a number!

Example
<!DOCTYPE html>
<html>
<head>
    <style>
        .demo{
            text-align: center;
            background-color: green;
            color: white;
            font-size: 50px;
        }
    </style>
</head>
<body>
    <h1>This is first heading</h1>
    <p class="demo">This is paragraph</p>
    <h2>This is second heading</h2>
    <h3 class="demo">This is third heading</h3>
</body>
</html>

Universal Selector

  • The universal selector (*) selects all HTML elements on the page.
Example
<!DOCTYPE html>
<html>
<head>
    <title></title>
    <style>
        *{text-align: center;
            background-color: seagreen;
            color: white;
            font-size: 20px;
        }
    </style>
</head>
<body>
    <h1>This is first heading</h1>
    <p>This is paragraph</p>
    <h3>This is third heading</h3>
    <h2>This is second heading</h2>
</body>
</html>

Grouping Selector

  • The grouping selector selects all the HTML elements with the same style definitions like the h1, h2, and p elements have the same style definitions. To group selectors, separate each selector with a comma.
Example
<!DOCTYPE html>
<html>
<head>
    <title></title>
    <style>
        h1,h3{
            text-align: center;font-size: 50px;
            color: white;background-color: rgb(11, 85, 244);
        }
        h2,p{
             text-align: right; color: green;
             font-size: xx-large;background-color: red;
        }
    </style>
</head>
<body>
<h1>This is a first heading</h1>
<p>This is a paragraph</p>
<h3>This is a third heading</h3>
<h2>This is a second heading</h2>
</body>
</html>
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