100 Fundamental CSS Interview Questions and Answers in Web and Mobile Development 2026

CSS is the language that adds style to web documents, such as layout, colors, and fonts. It plays a crucial role in web development by separating the content of a document (HTML) from its presentation. Understanding CSS is essential for every front-end developer, and interview questions about CSS are used to test a candidate’s ability to design and manipulate web layouts. These questions may revolve around topics like CSS selectors, box model, flex layout, grid layout, and responsive design. This blog post will provide answers to common CSS interview questions, which can help developers prepare for their next tech interview.

Content updated: January 1, 2024

CSS Basics

What does CSS stand for and what is its primary use?

Answer:

Cascading Style Sheets (CSS) is primarily designed to separate web page content from its visual presentation. This allows for a consistent and adaptable design across multiple web pages.

Key Concepts

Selectors: Elements to which the style rules apply.
Properties: Visual features, such as font-size, color, and background.
Values: Specific settings for properties, like ‘red’ for the color property.

Visual Example

Here is the HTML code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Example</title>
    <link rel="stylesheet" href="styles.css">
</head>
<body>
    <header>
        <h1>Welcome to Our Site</h1>
        <nav>
            <ul>
                <li><a href="#">Home</a></li>
                <li><a href="#">About</a></li>
                <li><a href="#">Contact</a></li>
            </ul>
        </nav>
    </header>
    <section>
        <h2>Latest News</h2>
        <article>
            <h3>Breaking News: Big Event Tomorrow</h3>
            <p>Join us for our biggest event of the year!</p>
        </article>
    </section>
    <footer>
        &copy; 2022 YourSite
    </footer>
</body>
</html>

And, here is the accompanying CSS in styles.css:

/* Targeting all text on the page */
body {
  font-family: Arial, sans-serif;
  color: #333;
  background-color: #f4f4f4;
}

/* Targeting the header elements */
header {
  background-color: #1e90ff;
  padding: 1em 0;
  text-align: center;
}

/* Targeting the nav elements */
nav ul {
  list-style-type: none;
  padding: 0;
}

/* Targeting the nav links */
nav a {
  text-decoration: none;
  color: #fff;
  margin: 0 10px;
}

/* Targeting the main section */
section {
  padding: 20px;
}

/* Targeting the footer element */
footer {
  text-align: center;
  margin-top: 50px;
  padding: 10px;
  background-color: #1e90ff;
  color: #fff;
}

2.
How do you include CSS in your HTML document?
Answer:
3.
Can you explain the difference between class and ID selectors?
Answer:
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4.
What are pseudo-classes in CSS?
Answer:
5.
Describe how to implement a CSS reset and why it is useful.
Answer:

Selectors and Combinators

6.
How do you select elements by attribute in CSS?
Answer:
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7.
What is a pseudo-element, and what are they used for?
Answer:
8.
Explain the difference between the child combinator and the descendant combinator.
Answer:
9.
How would you select all direct children elements of a particular type?
Answer:
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10.
What are the universal selector and the sibling combinator, and when would you use them?
Answer:

Box Model and Layout

11.
What is the CSS Box Model?
Answer:
12.
Explain margin collapsing.
Answer:
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13.
What are the different values for the box-sizing property and what do they do?
Answer:
14.
How do you center a block element with CSS?
Answer:
15.
What is the difference between block, inline, and inline-block elements?
Answer:

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100 Fundamental CSS Interview Questions

CSS Basics

What does CSS stand for and what is its primary use?

Key Concepts

Visual Example

How do you include CSS in your HTML document?

Can you explain the difference between class and ID selectors?

What are pseudo-classes in CSS?

Describe how to implement a CSS reset and why it is useful.

Selectors and Combinators

How do you select elements by attribute in CSS?

What is a pseudo-element, and what are they used for?

Explain the difference between the child combinator and the descendant combinator.

How would you select all direct children elements of a particular type?

What are the universal selector and the sibling combinator, and when would you use them?

Box Model and Layout

What is the CSS Box Model?

Explain margin collapsing.

What are the different values for the box-sizing property and what do they do?

How do you center a block element with CSS?

What is the difference between block, inline, and inline-block elements?

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