Design Principles for Developers: Processes and CSS Tips for Better Web Design

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It is technically true that anyone can cook. But there’s a difference between actually knowing how to prepare a delicious meal and hoping for the best as you throw a few ingredients in a pot. Just like web development, you might know the ingredients—<span>, background-color, .heading-1—but not everyone knows how to turn those ingredients into a beautiful, easy-to-use website.

Whenever you use HTML and CSS, you are designing—giving form and structure to content so it can be understood by someone else. People have been designing for centuries and have developed principles along the way that are applicable to digital interfaces today. These principles manifest in three key areas: how words are displayed (typography), how content is arranged (spacing), and how personalty is added (color). Let’s discover how to use each of these web design ingredients through the mindset of a developer with CSS properties and guidelines to take the guesswork out of web design.

Typography

Websites that are easy to read don’t happen by mistake. In fact, Taimur Abdaal wrote an entire article on the topic that’s chock-full of advice for developers working with type. We’re going to focus specifically on two fundamental principles of design that can help you display words in a more visually pleasing and easy-to-read way: repetition and hierarchy.

Use repetition for consistency and maintainability

Repetition comes fairly naturally on the web thanks to the importance of reusability in software. For example, CSS classes allow you to define a particular style for text and then reuse that style across the site. This results in repeating, consistent text styles for similar content which helps users navigate the site.

If, for example, you are working on styles for a new paragraph, first consider if there is existing content that has a similar style and try to use the same CSS class. If not, you can create a new class with a generic name that can be repeated elsewhere in your site. Think .paragraph--emphasize as opposed to .footer__paragraph--emphasize or .heading-1 as opposed to .hero__site-title. The first examples can be used across your site as opposed to the second which are scoped to specific components. You can even add a prefix like text- to indicate that the class is used specifically for text styles. This method will reduce the CSS file size and complexity while making it much easier to update global styles in the future.

In design, there are endless ways to experiment with styles. Designers can sometimes go a little crazy with their font styles by creating numerous slight variations of similar styles. However, in code, it’s valuable to restrict text styles to a minimum. Developers should urge designers to combine similar styles in order to reduce code weight and increase reusability and consistency.

Hierarchy provides a clear visual order to content

Hierarchy is something you really only notice when it’s not there. In typography, hierarchy refers to the visual difference between various pieces of text. It’s the distinction between headings, paragraphs, links, and other text styles. This distinction is made by choosing different fonts, colors, size, capitalization, and other properties for each type of text content. Good hierarchy makes complex information easier to digest and guides users through your content.

Out of the box, HTML provides some hierarchy (like how the font size of headings gets smaller as you go from <h1> to <h6>), but CSS opens the door for even more creativity. By giving <h1> tags an even larger font size, you can quickly establish greater difference in size between heading levels—and therefore more hierarchy. To create more variety, you can also change the color, text-align, and text-transform properties.

A note on choosing fonts

With typography, we need to make sure it is as easy to read as possible. The greatest overall factor in readability is the font you choose—which is a huge topic. There are many factors that determine how "readable" a font is. Some fonts are made specifically to be used as headings or short lines of text; these are called "display" fonts, and they often have more personality than fonts designed to be used for text. Unique flourishes and quirks make display fonts harder to read at small sizes and when part of a large paragraph. As a rule of thumb, use a more straightforward font for text and only use display fonts for headings.

If you’re in a pinch and need a readable font, try Google Fonts. Add a paragraph of text to the preview field and size it roughly how it will display on your website. You can then narrow down your results to serif or sans-serif and scan the list of fonts for one that is easy to read. Roboto, Noto Sans, Merriweather, and PT Serif are all very readable options.

CSS properties for better readability

• The main paragraph font-size should be between 16pxand 18px (1em and 1.25em) depending on the font you choose.
• Manually set line-height (the vertical space between two lines of text) to make your text less cramped and easier to read. Start with line-height: 1.25 (that is 1.25 times the font-size) for headings and at least 1.5 for paragraphs (but no more than 1.9) and adjust from there. The longer the line of text, the larger the line-height should be. To keep your text flexible, avoid adding a unit to your line-height. Without a unit the line-height you set will be proportional to your font-size. For example, line-height: 1.5 and font-size: 18px would give you a line height of 27 pixels. If you changed your font size to font-size: 16px on smaller screens, the computed line height would then change to 24 pixels automatically.

• Pay attention to how many characters are in a line of text and aim for 45 and 75 characters long (including punctuation and spaces). Doing so reduces reading fatigue for your users by limiting the eye and head movement needed to follow a line of text. With the variable nature of the web, it’s impossible to completely control line length, but you can use max-width values and breakpoints to prevent lines of text from getting too long. Generally speaking, the shorter the line of text, the faster it will be to scan for quick reading. And don’t worry too much about counting the characters in every line. Once you do it a few times, you’ll develop a sense for what looks right.

Spacing

After looking at typography, you can take a step back and examine the layout, or spacing, of your content. Movement and proximity are two design principles that relate to spacing.

Movement is about content flow

Movement refers to how your eye moves through the page or the flow of the page. You can use movement to direct a user’s eye in order to tell a story, point to a main action item, or encourage them to scroll. This is done by structuring the content within individual components and then arranging those components to form the layout of the page. By paying attention to how your eye moves through content, you can help users know where to look as they scan the page.

Unlike books, which tend to have very linear structure, websites can be more creative with their layout—in literally endless ways. It is important to make sure you are intentional with how you layout content and do so in a way which guides users through your content as easily as possible.

Consider these three examples above. Which is the easiest to follow? The arrangement on the left draws your eye off the screen to the left due to how the image is positioned which makes it hard to find the button. In the center option, it’s easy to skip over the headline because the image is too large in comparison. On the right, the heading draws your attention first and the image is composed so that it points to the main action item—the button.

White space is a helpful tool for creating strong movement, but it’s easy to use too much or too little. Think about how you are using it to direct the user’s eye and divide your content. When used well, users won’t notice the whitespace itself but will be able to better focus on the content you are presenting. For example, you can use whitespace to separate content (instead of a colored box) which results in a less cluttered layout.

Proximity establishes relationships

When objects are closer together, they are perceived as being related. By controlling spacing around elements, you can imply relationships between them. It can be helpful to create a system for spacing to help build consistency through repetition and avoid the use of random numbers. This system is based off the default browser font size (1rem or 16px) and uses distinct values that cover most scenarios:

• 0.25rem (4px)
• 0.5rem (8px)
• 1rem (16px)
• 2rem (32px)
• 4rem (64px)

You can use Sass or CSS variables so that the values are kept consistent across the project. A system might look like this—but use whatever you’re comfortable with because naming things is hard:

• $space-sm
• $space-med
• $space-lg
• $space-xl
• $space-xxl

Color conveys personality and calls attention

Color greatly affects a website’s personality. When used well, it gives pages life and emotion; used poorly, it can distract from the content, or worse, make it inaccessible. Color goes hand in hand with most design principles. It can be used to create movement by directing users’ eyes and can be used to create emphasis by calling attention to the most important action items.

A note on choosing colors

With color, it can be hard to know where to start. To help, you can use a four-step process to guide your color choices and build a color palette for the site.

Step 1: Know your mood

You have to know the mood or attitude of your site and brand before choosing colors. Look at your content and decide what you are trying to communicate. Is it funny, informative, retro, loud, somber? Typically, you can boil down the mood of your site to a few adjectives. For example, you might summarize The North Face as adventurous and rugged while Apple would be minimalistic and beautiful.

Step 2: Find your main color

With your mood in mind, try to visualize a color that represents it. Start with the color’s saturation (how intense the color is) and brightness (how close the color is to white or black). If your mood is upbeat or flashy, a lighter (more saturated) color is probably best. If your mood is serious or reserved, a darker (less saturated) color is better.

Next, choose a hue. Hue refers to what most people think of as colors—where does is fall on the rotation of the color wheel? The hue of a color is what gives it the most meaning. People tend to associate hues with certain ideas. For instance, red is often associated with power or danger and green relates to money or nature. It can be helpful to look at similar websites or brands to see what colors they use—although you don’t need to follow their lead. Don’t be afraid to experiment!

Step 3: Add supporting colors

Sometimes, two or three main colors are needed, but this is not necessary. Think about the colors of different brands. Some use a single color, and others have a main color and one or two that support it. Coca-Cola uses its distinct red. IKEA is mostly blue with some yellow. Tide is orange with some blue and yellow. Depending on your site’s mood, you might need a few colors. Try using a tool like Adobe Color or Coolors), both of which allow you to add a main color and then try different color relationships, like complementary or monochromatic, to quickly see if any work well.

Step 4: Expand your palette

Now that you’ve narrowed things down and found your main color(s), it’s time to expand your scope with a palette that gives your project versatility and constraint—here’s a methodology I’ve found helpful. Tints and shades are the trick here. Tints are made by mixing your main color(s) with white, and shades are made by mixing with black. You can quickly create an organized system with Sass color functions:

$main-color:          #9AE799;

$main-color-lightest: lighten($main-color, 20%);
$main-color-lighter:  lighten($main-color, 15%);
$main-color-light:    lighten($main-color, 10%);

$main-color-dark:     darken($main-color, 40%);
$main-color-darker:   darken($main-color, 50%);
$main-color-darkest:  darken($main-color, 60%);

To round out your palette, you’ll need a few more colors, like a white and black. Try creating a "rich black" using a dark, almost black shade of your main color and, on the other end of the spectrum, pick a few light grays that are tinted with your main color. Tinting the white and black adds a little more personality to your page and helps create a cohesive look and feel.

Last but not least, if you are working on an interactive product, you should add colors for success, warning, and error states. Typically a green, yellow, and red work for these but consider how you can adjust the hue to make them fit better with your palette. For example, if your mood is friendly and your base color is green, you might want to desaturate the error state colors to make the red feel less negative.

You can do this with the mix Sass color function by giving it your base color, the default error color, and the percentage of base color that you want to mix in with the error color. Adding desaturate functions helps tone down the colors:

$success: mix($base-color, desaturate(green, 50%), 50%);
$warning: mix($base-color, desaturate(yellow, 30%), 5%);
$error:   mix($base-color, desaturate(red, 50%), 20%);

When it comes to the web, there’s one color principle that you have to pay extra attention to: contrast. That’s what we’ll cover next.

Contrast

Color contrast—the difference in saturation, brightness, and hue between two colors—is an important design principle for ensuring the web is accessible to those with low vision or color blindness. By ensuring there is enough contrast between your text and whatever is behind it on your site will be more accessible for all sighted users. When looking at accessibility, be sure to follow the color contrast guidelines provided by W3C’s Web Content Accessibility Guidelines (WCAG). There are many tools that can help you follow these guidelines, including the inspect panel in Chrome’s dev tools.

Now, it’s time to put these principles to practice! You can use these processes and CSS tips to help take the guesswork out of design and create better solutions. Start with what you are familiar with, and eventually, the design principles mentioned here will become second nature.

If you’re looking for even more practical tips, Adam Wathan and Steve Schoger wrote about some of their favorites.

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