Hiring guide for CSS Engineers

CSS Developer Hiring Guide

CSS (Cascading Style Sheets) is a computer programming language developed in 1996 by the World Wide Web Consortium (W3C) to enhance HTML's design capabilities. It is primarily used for describing the look and formatting of a document written in HTML or XML. CSS enables developers to control layout, colors, fonts, and other aspects of web pages that previously could only be partially manipulated through HTML. Over time, CSS has evolved into three levels: CSS1, CSS2, and CSS3 - each introducing new features and improvements over its predecessor. Its widespread adoption across web browsers underscores its pivotal role in modern web design.

Ask the right questions secure the right CSS talent among an increasingly shrinking pool of talent.

First 20 minutes

General CSS app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in CSS application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are CSS selectors?
CSS selectors are patterns used to select the element(s) you want to style. They can select elements based on their name, id, class, attribute, and more.
How would you include a CSS file in HTML?
You can include a CSS file in HTML using the tag in the section of the HTML file. The href attribute should contain the path to the CSS file.
Describe the difference between 'class' and 'id' in CSS.
In CSS, 'class' can be used to select and style multiple elements, while 'id' is used to select and style a single unique element. 'id' has a higher specificity than 'class'.
What is the CSS box model?
The CSS box model is a box that wraps around every HTML element. It consists of: the content, padding, border, and margin.
What are pseudo-classes in CSS?
Pseudo-classes in CSS are used to define a special state of an element. For example, :hover can be used to change a button's color when the user's pointer hovers over it.
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What you’re looking for early on

Does the candidate have a strong understanding of CSS fundamentals?
Has the candidate demonstrated the ability to solve problems?
Is the candidate familiar with responsive design principles?
Can the candidate work well with others?

Next 20 minutes

Specific CSS development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you create a CSS rule that applies to multiple selectors?
You can create a CSS rule that applies to multiple selectors by separating each selector with a comma. For example, 'h1, h2, p { color: red; }' applies the same style to h1, h2 and p elements.
What is the difference between 'block' and 'inline' display values in CSS?
In CSS, 'block' elements start on a new line and take up the full width, while 'inline' elements can start on the same line and only take up as much width as necessary.
What are CSS media queries?
CSS media queries are a technique used for making responsive web designs. They allow you to apply different styles based on the characteristics of the device rendering the web page, such as screen width.
How would you use CSS to make a website responsive?
To make a website responsive with CSS, you can use media queries to apply different styles for different screen sizes. You can also use relative units instead of fixed units, and use the viewport meta tag.
Describe the difference between 'relative', 'fixed', 'absolute', and 'sticky' positioning in CSS.
'Relative' positioning is positioned relative to its normal position. 'Fixed' positioning is positioned relative to the browser window. 'Absolute' positioning is positioned relative to the nearest positioned ancestor. 'Sticky' positioning is a hybrid of relative and fixed positioning.
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The ideal back-end app developer

What you’re looking to see on the CSS engineer at this point.

At this point, a skilled CSS engineer should demonstrate strong problem-solving abilities, proficiency in CSS programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with CSS.

What does the following CSS code do?
p {
 color: red;
This code snippet will make the text color of all paragraph elements ('p') red.
What does the following CSS code do?
.container {
 display: flex;
 flex-direction: column;
This code snippet applies a flex container layout to all elements with the class 'container'. The flex-direction property is set to column, which means the flex items will be laid out in a column, from top to bottom.
What does the following CSS code do?
#nav li {
 display: inline-block;
This code snippet will make all list items ('li') that are children of the element with the id 'nav' display as inline-block. This means that the list items will line up horizontally, but still retain block properties.
What does the following CSS code do?
h1 + p {
 margin-top: 0;
This code snippet will remove the top margin from any paragraph ('p') that directly follows a heading 1 ('h1') element. The '+' is an adjacent sibling combinator, which selects only the specified element that immediately follows the former specified element.

Wrap-up questions

Final candidate for CSS Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle CSS application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are CSS preprocessors and why are they useful?
CSS preprocessors, like Sass and LESS, allow developers to write CSS in a more programming-like way with features like variables, nesting, and mixins. They are useful because they can make CSS more maintainable and easier to write.
How would you implement a CSS reset?
A CSS reset can be implemented by creating a CSS file that sets the margins, padding, and other properties of all elements to a consistent baseline value. This file should be linked in the HTML before any other CSS files.
What is the difference between 'em' and 'rem' units in CSS?
Both 'em' and 'rem' are scalable units in CSS. 'em' is relative to the font-size of its closest parent, while 'rem' is only relative to the root (html) font-size.

CSS application related

Product Perfect's CSS development capabilities

Beyond hiring for your CSS engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in CSS projects, and can engage in multiple capacities.