What is CSS (Cascading Style Sheets) in Simple Words?

Cascading Style Sheets, commonly referred to as CSS, is a fundamental technology for web development that plays a crucial role in the presentation and styling of web content.

CSS allows web developers to control the layout, design, and appearance of HTML elements, making websites visually appealing and user-friendly.

In this article, we will explore CSS in-depth, covering its purpose, syntax, selectors, properties, and practical applications.

Table of Contents #
  1. Introduction to CSS
  2. The Purpose of CSS
  3. CSS Syntax
  4. CSS Selectors
  5. CSS Properties
  6. Practical Applications of CSS
  7. Conclusion

1. Introduction to CSS

CSS, which stands for Cascading Style Sheets, is a stylesheet language used to describe the visual presentation of web documents, including HTML and XML documents.

CSS was first introduced in 1996 as a way to separate the structure and content of a web page (HTML) from its visual styling.

This separation allows web developers to define the appearance of a web page without altering its underlying content.

2. The Purpose of CSS

The primary purpose of CSS is to control the design and layout of web content. Here are some of its key functions:

  • Styling: CSS is used to apply fonts, colors, backgrounds, and spacing to text and elements on a web page.
  • Layout: CSS allows developers to define the placement and sizing of elements, creating responsive and visually appealing layouts.
  • Consistency: It ensures a consistent look and feel across a website by providing a single source of styling rules.
  • Accessibility: CSS can be used to improve the accessibility of web content by controlling text size, contrast, and more.
  • Print-Friendly Styles: CSS can provide separate styles for printed versions of web pages, ensuring they are optimized for the printed medium.
HTML layout after adding css
HTML layout without CSS

3. CSS Syntax

CSS consists of rules that define how specific elements in an HTML document should be styled. Each rule is made up of a selector and a declaration block.

The basic syntax of a CSS rule is as follows:

selector {
    property: value;
  • Selector: The selector specifies which HTML elements the rule should apply to. For example, h1 targets all <h1> elements, and .class targets elements with a specific class, while #id targets elements with a specific ID.
  • Property: The property is the CSS attribute you want to change, like color, font-size, or background-color.
  • Value: The value is the setting you want to apply to the property, such as red, 16px, or #FFFFFF.

Learn: How to write and add CSS in HTML pages?

4. CSS Selectors

CSS selectors are patterns used to select and style elements on a web page. They help determine which elements a CSS rule should apply to.

There are various types of selectors:

4.1. Type Selectors

Type selectors match HTML elements by their element type. For example, h1 selects all <h1> elements on the page.

/* It selects all <h1> elements on the page */
h1 {
    /* Styles */

4.2. Class Selectors

Class selectors select elements based on their class attribute. For example, .button targets elements with the class “button.”

<a class="button" href="#">Hello</a>
<span class="button">Hi</span>
/* This selector targets elements with the class "button." */
    /* Styles */

4.3. ID Selectors

ID selectors target elements with a specific ID attribute. For example, #header selects an element with the ID “header.”

/* <div id="header">Welcome</div> */ 


4.4. Universal Selectors

The universal selector * selects all elements on a page. It is often used to reset default styles.

/* selects all elements on a page */

4.5. Attribute Selectors

Attribute selectors allow you to target elements based on their attributes. For example, [target="_blank"] selects all elements with the target attribute set to “_blank.”

/* <a href="#" target="_blank">Hello</a> */



4.6. Pseudo-Class and Pseudo-Element Selectors

Pseudo-classes and pseudo-elements are used to select elements in specific states or parts of an element.

For example, :hover selects elements when the mouse is over them, and ::before creates a pseudo-element before the content of an element.





5. CSS Properties

CSS provides a wide range of properties to control the visual appearance of HTML elements. Here are some common categories of CSS properties:

5.1. Color Properties

Color properties, such as color, background-color, and border-color, are used to control the color of text and background.

    p {
        background-color: green;
        color: white;
        border: 3px solid red;
<p>Hello, This is a paragraph.</p>
CSS Background color, border colro and text color result

5.2. Text Properties

Text properties, including font-family, font-size, and text-align, define how text is displayed.

    p {
        border: 3px solid black;
        text-align: center;
        font-size: 32px;
        font-family: system-ui;
<p>Hello CSS</p>
css text align center, border, font size example

5.3. Font Properties

Font properties like font-weight, font-style, and text-transform allow you to adjust the appearance of text.

    p {
        border: 3px solid black;
    .bold {
        font-weight: bold;
    .it {
        font-style: italic;
    .uc {
        text-transform: uppercase;
    <span class="bold">Bold</span>, <span class="it">Italic</span>, and
    <span class="uc">Uppercase</span>
css bold italic and uppercase example

5.4. Box Properties

Box properties, such as width, height, and border, define the size and border of elements.

    div {
        border: 3px solid black;
        width: 200px;
        height: 100px;
<div>Width, Height, Border</div>
css border width height example

5.5. Margin and Padding Properties

Margin and padding properties, like margin and padding, control the spacing around elements.

5.6. Background Properties

Background properties, including background-image, background-repeat, and background-position, define the background appearance of elements.

Practical Applications of CSS

CSS is extensively used in web development for various purposes:

6.1. Styling Text and Fonts

CSS is used to style text, change font properties, and enhance the readability of web content.

6.2. Creating Responsive Layouts

Web developers use CSS to create responsive designs that adapt to different screen sizes and devices.

6.3. Designing Navigation Menus

CSS plays a crucial role in designing navigation menus, dropdowns, and other interactive elements.

6.4. Applying Animation and Transitions

Advanced CSS techniques like keyframe animations and transitions are used to create interactive and visually engaging web applications.


CSS, or Cascading Style Sheets, is a vital technology in web development that empowers developers to control the design, layout, and appearance of web content.

By understanding CSS syntax, selectors, and properties, web developers can create visually appealing, responsive, and user-friendly websites.

CSS continues to evolve, and staying up-to-date with the latest CSS features and best practices is essential for creating modern web applications.