10 CSS Interview Questions (And Answers) to Test Your Knowledge

Written by Coursera Staff • Updated on

Think you know CSS? Check out these 10 CSS interview questions to test your knowledge and see if you’re ready for your next big interview.

[Featured Image] Two men standing in an office shaking hands before an interview where they will discuss css interview questions.

Without Cascading Style Sheets (CSS), the internet would likely be a boring place—or a less visually appealing one. Not only is CSS amongst the easiest programming languages to learn, according to ZDNet [1], but it's also a simple way to bring websites to life, create seamless customisation, and enhance the user experience while making mobile-friendly websites.

If you’re going into web development or design, content management, or project management, CSS is one of the essential programming languages you should know. Are you considering entering one of these roles or preparing for a job interview? These 10 CSS interview questions can help gauge your readiness and guide your next steps. 

1. How can you add CSS to an HTML document? 

What they’re really asking: 

You can add CSS in three ways: external, inline, and internal. The most common way to add CSS to HTML pages or documents is using an external style sheet that you add via a link in the HTML page’s <head> section to link it to an external CSS file. Inline CSS lets you apply a specific style within a particular HTML element using the style attribute in that element. Internal 

CSS makes it possible to define a single HTML page’s style in the page’s <head> section and <style> element.

CSS frameworks offer a selection of tools to make front-end development and design fast and easy. Popular options include beginner-friendly Tailwind CSS, which features pre-designed menus of widgets, integrated tutorials, and modular components that allow you to make changes in particular areas without impacting the entire code. In 2011, Twitter introduced Bootstrap, one of the most popular CSS frameworks because of its features, including ready-to-use components, stellar support by a community of developers, and easy customisation. 

The foundation's mobile-first framework, which includes a jQuery package, helps create responsive emails and websites. It is also lightweight and has various configurable components and unique features, such as custom forms and an aesthetic design with drag-and-drop options for email.

3. What are some pros and cons of using CSS?

CSS makes it possible to create attractive web pages using less code, which translates to faster page speeds. A few pros and cons include:

Pros:

  • Improved user experience with user-friendly design and formatting

  • Fast development with the ability to replicate multiple pages using a single string of code

  • Easy changes to formatting without the need to fix every page by making changes on the specific CSS stylesheet

  • Responsive design allows you to optimise content across all devices

  • No need to download style sheets every time you want to use them. Store style sheets in the browser cache to use on multiple pages. 

Cons: 

  • Lack of ability to select parent tags

  • Because CSS comes in multiple levels, it can create confusion

  • Developers must perform compatibility tests because CSS creates fragmentation—everything doesn't work the same across every browser

  • CSS is an open system that doesn't include integrated security

4. What is an embedded style sheet, and why would you use it?

Using embedded style sheets, you can define an HTML’s styles in a single spot using the <style> element. It’s an alternative to external style sheets that allow you to handle HTML documents with unique style requirements. It offers multiple advantages, including applying styles in complex HTML documents relatively easily using grouping and selector methods. Embedded style sheets also facilitate creating classes you can use on multiple tag types and import information without performing additional downloads.

5. Define RGB and how you would use it in CSS.

RGB represents colours in CSS: red, green, and blue. You use parameters ranging from 0 to 256 to define the intensity of those colours. Using this colour model, you can add red, green, and blue lights to reproduce hues like maroon, fuchsia, aqua, olive, grey, silver, navy, black, and more. You write the rgb() function as rgb (number, number, number). Each number within the parenthesis corresponds to a percentage value and intensity of that specific colour.

6. What is the Z index?

Z-index is a property in CSS that allows you to define the order in which elements overlap. Elements with a higher index value stack above elements with z-index values. For example, you can use the Z-index to change the order of colours or to place background elements under other elements. 

7. Briefly explain CSS image sprites.

CSS sprites are essential for loading multiple images with unseen blinking and advanced asset downloading that takes place when needed. This collection of images is combined into one image, reducing the bandwidth and required server requests for web pages with various images. It also reduces load time. The basic function is ‘img_navsprites.gif,’ and you can specify the part of the image to display. CSS image sprites also make it possible to create navigation lists with or without a hover effect. 

8. What are Sass, Less, and Stylus?

Sass, Less, and Stylus are CSS preprocessor tools that help extend CSS’s functionality, allowing you to use variables, mixins, and other complex logical syntax. Syntactically Awesome Style Sheets (Sass) doesn’t use curly brackets or semicolons. It is based on indentation and uses the .sass extension. Leaner Style Sheets (Less) uses the .less extension and allows you to specify what you see. It follows declarative styling patterns and enhances CSS with minimal additional features, making it readable and easy to understand. Stylus has an imperative syntax similar to Sass but with additional expressiveness and flexibility. 

9. How many media types does CSS allow?

The style sheets in CSS specify how documents should appear on various media. Some properties work best with specific media, while others may work on multiple media but require different values. CSS allows seven types of media, including: 

  • Audio

  • Visual

  • Speech

  • Tactile (like braille, for example)

  • Continuous or pages

  • Bitmap or grip

  • Interactive

10. Can you define responsive web design and the role CSS plays?

Responsive web design uses layouts, media queries, and images that are flexible enough to respond to the user’s environment and behaviour, allowing the design to remain optimised on any screen size or platform. It’s the secret to design that flows seamlessly from desktop to mobile device.  This design strategy relies on various CSS layout techniques, including Grid Layout and Flexbox, and CSS media queries that make it easy to adapt styles to the device viewing the content for an optimal user experience.

Next steps

Now that you’re more familiar with the CSS interview questions a potential employer may ask, ask yourself one more: Are you ready to start applying for jobs? If not, consider strengthening your knowledge and skills to prepare. Online options include Web Design for Everybody: Basics of Web Development & Coding, a specialisation offered by the University of Michigan on Coursera. Within three to six months, beginners can gain proficiency using CSS, HTML, Javascript, and more to design web pages, add interactive elements, and apply responsive design.

If you want to brush up on your skills or gain extra experience in using CSS, consider a Guided Project such as Style Images with CSS on Coursera Project Network.

Article sources

  1. ZDNet. “The easiest programming languages to learn, https://www.zdnet.com/education/computers-tech/easiest-programming-languages-to-learn/.” Accessed 8 April 2024.

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