8 top skills for advanced CSS developers

If you’re reading this, you probably already know that Cascading Style Sheets (CSS) enable front-end developers and designers to define the style of a website or web application. 

This creates a visually appealing product for your site visitors, and as 50% of consumers say that website design is crucial when it comes to their opinions of a brand, it’s not something that can be ignored.

CSS is a specific language that cannot exist without HyperText Markup Language (HTML) to make sense of it all. So, if you’re looking for a CSS developer you need one who has mastered skills like HTML, as well as basic and more advanced CSS. 

We’re going to take a look at the top advanced skills CSS developers should have, and how you can test CSS skills in an accurate, fair, and unbiased way with TestGorilla’s CSS test.

Let’s take a dive into the world of advanced CSS skills and the CSS test, but first, we’ll take a detour and find out what advanced CSS is.

What is advanced CSS?

You need a modern and responsive website for your brand, and advanced CSS is the box of tricks that can help bring your site’s frontend into the 21st century.

Website design has changed to make it an easier and more enjoyable experience for mobile device users – and there’s a lot of them worldwide. Around 96% of internet users go online on their mobiles, so responsive web design is crucial. Advanced CSS skills help a developer make websites that are responsive and appealing, whatever size of device they are being viewed on. 

Learning advanced CSS tests the skills of a developer, enabling them to structure web pages quickly and more efficiently, and to get the job done by using less code. 

Another bonus of having advanced CSS skills is that any code a developer writes is more organized and easily understood, which is essential if they are working as part of a team. 

1. CSS preprocessors

CSS preprocessors sound complicated to those of us who don’t know much about web development and design. In a nutshell, CSS preprocessors are scripting languages used to extend the default capabilities of CSS. 

Popular CSS preprocessors are Sass, Stylus, and LESS, but there are other ones out there. All these preprocessors do similar tasks in different ways, and they have advanced features that are specific to them. They have their own ecosystems such as tools, libraries, and frameworks, so a CSS developer should have experience in using them.

CSS preprocessors enable a developer to use logic like variables, nesting, mixins, functions, and inheritance in their CSS code. They are great for creating reusable code snippets, reducing the number of errors, and can automate repetitive tasks and ensure backward compatibility.

2. CSS custom properties

Advanced developers don’t always need CSS preprocessors to use variables within their code. There’s another way to do it, and that’s with CSS Custom Properties.

CSS Custom Properties enable you to define and use variables within your code, reducing the need to repeat yourself. There are other benefits to using CSS Custom Properties, and they include:

• Cascading: Easily override values in selectors

• Native support: No need for a preprocessor

• Live updates: Change values in media queries and access variables in JavaScript

If a developer knows how to use CSS preprocessors, they don’t strictly need to know about CSS Custom Properties, but it shows an advanced understanding of CSS.

3. Layout and display with flexbox

Back in the day, web developers had to have some tricks up their sleeves to get sites to look good.

Web design is ever-evolving, and now that CSS3 is being used a new concept is on the scene: The Flexible Box (flexbox). 

Flexbox was created as a one-dimensional layout model, and it enables space distribution between interface items. It also offers alignment capabilities. 

Flexbox deals with layout in one dimension, which is either a row or a column. In contrast, the two-dimensional model of CSS grid layout controls columns and rows at the same time.

Those who work with a flexbox need to have skills that include working with:

• Flex containers

• Flex items

• Flex lines

• Changing flex-direction 

• Start and end lines

• Multi-line flex containers with flex-wrap

• Flex-flow shorthand

• Alignment, justification, and distribution of free space between items

4. CSS responsiveness

As we mentioned earlier, knowing how to create responsive web pages for all kinds of devices is essential. Responsive web design isn’t a technology, and can only be created with knowledge of CSS and HTML.

Making a website fit a mobile device screen shouldn’t mean leaving things out, but instead, it should respond and adapt the content to fit any device. Fluid grids and fluid images along with media queries make this possible, so CSS developers need to know when and how to implement these.

To be skilled in creating responsive sites, a web developer should also have knowledge of:

• Flexible grids

• Modern layout technologies

• The viewport meta tag

• Responsive images

• Responsive typography

5. Styling text

The ability to style text for a website is essential, as it’s one of the most common tasks a web designer does. The size and way that text is arranged on the screen matters. It’s one of the most important factors in whether visitors will stick around to read your content.

Did you know that there are only a certain number of fonts generally available across all systems? It’s not like using Word or Google Docs with their huge selection of fonts; there are specific web-safe fonts used by developers and designers, and these can be used without problems.

The reason for this lack of fonts is that the developer may not know which fonts are available on the website viewer’s computer or mobile device. 

Web-safe fonts are generally universal and include fonts like Arial and Times New Roman. These fonts are available on nearly all of the most commonly used operating systems, such as Windows, macOS, common Linux distributions, iOS, and Android.

Many designers hate being stuck with such a narrow choice of fonts, so there is a way to use CSS to create a specific web font of your choice. 

CSS enables you to choose font files that are available on the web. These are then downloaded along with your website when a viewer accesses it, and they can see your fonts of choice with no problems if they are using a browser that supports this CSS feature.

To style fonts successfully, a CSS developer must know about:

• Setting font-weight

• Font families and styles

• Font color

• Font shorthand

• Text alignment

• Line spacing

• Letter spacing

• Implementing code for creating web fonts

6. CSS units and values

What if you need to show numbers, percentages, and lengths on a website? There are several numeric and textual value types a developer will work with when using CSS.

All CSS declarations include a pair: property/value. The value can include a keyword or integer (whole number), or even a series of keywords and values with units or without. 

There are a set of values and units data types that CSS properties will work with, so a skilled CSS developer should know them:

• Absolute length units

• Relative length units

• Percentages

• Numbers

• Color keywords

• Hexadecimal RGB values

• RGB and RGBA values

• HSL and HSLA values

• Images

• Strings and identifiers

• Position

7. CSS animations

Is it possible to animate items on a webpage without slowing it down? Yes; and an advanced CSS developer can do it with ease.

Traditional animations on websites were script-driven, but CSS animations have three advantages over them:

1. They’re easy to use if you want to create simple animations.

2. The animations run smoothly compared to simple animations in JavaScript, even if there is a fair amount of system load.

3. If the browser controls the animation sequence it can optimize performance and efficiency automatically.

Pure CSS animations don’t need extra code or media added to them, as everything is done with HTML and CSS. Websites are looking to add dynamic, interesting content without slowing loading speeds down, so CSS animations are a good choice as they don’t carry extra scripts.

A web designer can create a whole host of useful website animations, from a mouse-hover transition effect to an opening envelope animation or a toggle switch.

To make a CSS animation as a developer, you should have four things: 

• an HTML element to animate

• a CSS rule which binds the animation  

• a group of keyframes that defines the start and end styles of the animation, as well as at the start and end of the animation. 

• Declarations for animation speed, delay, and duration to customize your animation

8. CSS selectors

As a web developer, you’ll need to be able to define the HTML elements on the web pages that you want to style with CSS. That’s where selectors come in. They tell a browser which elements should have CSS property values applied to them.

There are a lot of CSS selectors out there, which is good because it allows for precision work when selecting elements for styling. In order to understand and use CSS selectors, a developer needs to have a good grasp of the different selector types:

• Type, class, and ID

• Attribute selectors

• Pseudo-classes and pseudo-elements

• Combinators

Is there a reliable way to test CSS skills?

Yes, there is. Skills-based testing with an accurate CSS test is a fairer and faster way to start the hiring process, and there’s no need to waste your time on CVs. 

TestGorilla’s CSS Developer test has been created by a subject-matter expert, and it covers three key areas of CSS:

The CSS test can be used as part of the hiring process for CSS developers, front-end developers, and for anyone else who needs to know CSS as part of their role.

At TestGorilla, we constantly review our tests, so you can be sure you’re getting the most up-to-date questions in the CSS test when something in the coding changes.

Below are a couple of sample questions to give you a better understanding of how the CSS test works:

The first question in the CSS test above evaluates how much candidates know about adding borders, and the second question in the CSS test looks at their understanding of div elements.

If a candidate scores highly on the CSS test, you can be assured they have a strong grasp of CSS and its associated techniques, tools, and principles to create responsive and appealing websites. 

They are also able to fix bugs on the front-end during development and they are able to implement a design without using unnecessarily complex code, which is a real bonus when you need a web developer to work as part of a team.

How TestGorilla assessments work with the CSS test

It’s not enough to hire a brilliant CSS developer based on CSS tests alone. To get a more nuanced view of their technical and soft skills, you need to give them a range of tests all in one assessment.

TestGorilla enables you to add up to five tests to an assessment, and we recommend you add custom questions too. It’s important to use tests and assessments as the first step in your hiring process for maximum efficiency. 

For a more in-depth look at the reasons for this, you might want to take a look at our blog post on why pre-employment testing should be done at the very start of your recruitment drive.

You may choose to add more programming tests to complement the CSS test, depending on the role you want a developer to take. This could be the Java (Coding) Debugging test, which gives candidates 30 minutes to read through the requirements and then fix a partially working script.

However, we recommend also adding a Personality and Culture test, as well as important soft skills tests like the Communication test, which evaluates candidates on their ability to communicate effectively in written and verbal forms. A developer must be able to communicate well in order to work within a team. 

The Time Management test will also show how candidates deal with working to deadlines and managing time in a professional environment, which is another essential skill for developers.

The Culture Add test will help you see how applicants align with your organization’s values and behaviors. This test is customizable so you can create questions that reflect the values of your brand.

Use TestGorilla to find the best CSS developers

TestGorilla gives you the information and the tools needed to build effective assessments and evaluate real-life job skills and soft skills for CSS developers. 

The TestGorilla CSS test for developers is just one of the many tests for programming skills available in our test library. When you combine the our CSS test with a selection of our other tests, you have a powerful hiring tool that assists you to choose the top-ranking candidates based on their skills, instead of an outmoded CV.

Skills-based hiring is the future of recruitment. It frees you from the shackles of the CV as an (inaccurate) measure of a candidate’s skills and job success.

Take a closer look at our CSS test, check out our pricing plan page to see which option is right for you, or get started with a free plan today. You might even decide to create an assessment to take yourself. It’s a fun and informative way to get first-hand insight into the TestGorilla candidate experience.