CSS Protips

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A collection of tips to help take your CSS skills pro.

Use a CSS Reset Jump to heading

CSS resets help enforce style consistency across different browsers with a clean slate for styling elements. You can use a CSS reset library like Normalize, et al., or you can use a more simplified reset approach:

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

    

Now elements will be stripped of margins and padding, and box-sizing lets you manage layouts with the CSS box model.

Demo

Note: If you follow the Inherit box-sizing tip below you might opt to not include the box-sizing property in your CSS reset.

Inherit box-sizing Jump to heading

Let box-sizing be inherited from html:

html {
  box-sizing: border-box;
}

*,
*::before,
*::after {
  box-sizing: inherit;
}

    

This makes it easier to change box-sizing in plugins or other components that leverage other behavior.

Demo

Use unset Instead of Resetting All Properties Jump to heading

When resetting an element’s properties, it’s not necessary to reset each individual property:

button {
  background: none;
  border: none;
  color: inherit;
  font: inherit;
  outline: none;
  padding: 0;
}

    

You can specify all of an element’s properties using the all shorthand. Setting the value to unset changes an element’s properties to their initial values:

button {
  all: unset;
}

    

Note: the all shorthand isn’t supported in IE11 and is currently under consideration for support in Edge. unset isn’t supported in IE11.

Use :not() to Apply/Unapply Borders on Navigation Jump to heading

Instead of putting on the border…

/* add border */
.nav li {
  border-right: 1px solid #666;
}

    

…and then taking it off the last element…

/* remove border */
.nav li:last-child {
  border-right: none;
}

    

…use the :not() pseudo-class to only apply to the elements you want:

.nav li:not(:last-child) {
  border-right: 1px solid #666;
}

    

Here, the CSS selector is read as a human would describe it.

Demo

Check If Font Is Installed Locally Jump to heading

You can check if a font is installed locally before fetching it remotely, which is a good performance tip, too.

@font-face {
  font-family: 'Dank Mono';
  src:
    /* Full name */ local('Dank Mono'), /* Postscript name */ local('Dank Mono'),
    /* Otherwise, download it! */ url('//...a.server/fonts/DankMono.woff');
}

code {
  font-family: 'Dank Mono', system-ui-monospace;
}

    

H/T to Adam Argyle for sharing this protip and demo.

Add line-height to body Jump to heading

You don’t need to add line-height to each <p>, <h*>, et al. separately. Instead, add it to body:

body {
  line-height: 1.5;
}

    

This way textual elements can inherit from body easily.

Demo

Set :focus for Form Elements Jump to heading

Sighted keyboard users rely on focus to determine where keyboard events go in the page. Make focus for form elements stand out and consistent then a browser’s default implementation:

a:focus,
button:focus,
input:focus,
select:focus,
textarea:focus {
  box-shadow: none;
  outline: #000 dotted 2px;
  outline-offset: 0.05em;
}

    

Demo

Vertically-Center Anything Jump to heading

No, it’s not black magic, you really can center elements vertically. You can do this with flexbox…

html,
body {
  height: 100%;
  margin: 0;
}

body {
  align-items: center;
  display: flex;
}

    

…and also with CSS Grid:

body {
  display: grid;
  height: 100vh;
  margin: 0;
  place-items: center center;
}

    

Want to center something else? Vertically, horizontally…anything, anytime, anywhere? CSS-Tricks has a nice write-up on doing all of that.

Note: Watch for some buggy behavior with flexbox in IE11.

Demo

Comma-Separated Lists Jump to heading

Make list items look like a real, comma-separated list:

ul > li:not(:last-child)::after {
  content: ',';
}

    

Use the :not() pseudo-class and no comma will be added to the last item.

Note: This tip may not be ideal for accessibility, specifically screen readers. And copy/paste from the browser doesn’t work with CSS-generated content. Proceed with caution.

Select Items Using Negative nth-child Jump to heading

Use negative nth-child in CSS to select items 1 through n.

li {
  display: none;
}

/* select items 1 through 3 and display them */
li:nth-child(-n + 3) {
  display: block;
}

    

Or, since you’ve already learned a little about using :not(), try:

/* select all items except the first 3 and display them */
li:not(:nth-child(-n + 3)) {
  display: block;
}

    

Demo

Use SVG for Icons Jump to heading

There’s no reason not to use SVG for icons:

.logo {
  background: url('logo.svg');
}

    

SVG scales well for all resolution types and is supported in all browsers back to IE9. Ditch your .png, .jpg, or .gif-jif-whatev files.

Note: If you have SVG icon-only buttons for sighted users and the SVG fails to load, this will help maintain accessibility:

.no-svg .icon-only::after {
  content: attr(aria-label);
}

    

Use the “Lobotomized Owl” Selector Jump to heading

It may have a strange name but using the universal selector (*) with the adjacent sibling selector (+) can provide a powerful CSS capability:

* + * {
  margin-top: 1.5em;
}

    

In this example, all elements in the flow of the document that follow other elements will receive margin-top: 1.5em.

For more on the “lobotomized owl” selector, read Heydon Pickering’s post on A List Apart.

Demo

Use max-height for Pure CSS Sliders Jump to heading

Implement CSS-only sliders using max-height with overflow hidden:

.slider {
  max-height: 200px;
  overflow-y: hidden;
  width: 300px;
}

.slider:hover {
  max-height: 600px;
  overflow-y: scroll;
}

    

The element expands to the max-height value on hover and the slider displays as a result of the overflow.

Equal-Width Table Cells Jump to heading

Tables can be a pain to work with. Try using table-layout: fixed to keep cells at equal width:

.calendar {
  table-layout: fixed;
}

    

Pain-free table layouts.

Demo

Get Rid of Margin Hacks With Flexbox Jump to heading

When working with column gutters you can get rid of nth-, first-, and last-child hacks by using flexbox’s space-between property:

.list {
  display: flex;
  justify-content: space-between;
}

.list .person {
  flex-basis: 23%;
}

    

Now column gutters always appear evenly-spaced.

Use Attribute Selectors with Empty Links Jump to heading

Display links when the <a> element has no text value but the href attribute has a link:

a[href^='http']:empty::before {
  content: attr(href);
}

    

That’s pretty convenient.

Demo

Style “Default” Links Jump to heading

Add a style for “default” links:

a[href]:not([class]) {
  color: #008000;
  text-decoration: underline;
}

    

Now links that are inserted via a CMS, which don’t usually have a class attribute, will have a distinction without generically affecting the cascade.

Consistent Vertical Rhythm Jump to heading

Use a universal selector (*) within an element to create a consistent vertical rhythm:

.intro > * {
  margin-bottom: 1.25rem;
}

    

Consistent vertical rhythm provides a visual aesthetic that makes content far more readable.

Intrinsic Ratio Boxes Jump to heading

To create a box with an intrinsic ratio, all you need to do is apply top or bottom padding to a div:

.container {
  height: 0;
  padding-bottom: 20%;
  position: relative;
}

.container div {
  border: 2px dashed #ddd;
  height: 100%;
  left: 0;
  position: absolute;
  top: 0;
  width: 100%;
}

    

Using 20% for padding makes the height of the box equal to 20% of its width. No matter the width of the viewport, the child div will keep its aspect ratio (100% / 20% = 5:1).

Demo

Style Broken Images Jump to heading

Make broken images more aesthetically-pleasing with a little bit of CSS:

img {
  display: block;
  font-family: sans-serif;
  font-weight: 300;
  height: auto;
  line-height: 2;
  position: relative;
  text-align: center;
  width: 100%;
}

    

Now add pseudo-elements rules to display a user message and URL reference of the broken image:

img::before {
  content: "We're sorry, the image below is broken :(";
  display: block;
  margin-bottom: 10px;
}

img::after {
  content: '(url: ' attr(src) ')';
  display: block;
  font-size: 12px;
}

    

Learn more about styling for this pattern in Ire Aderinokun’s original post.

Use rem for Global Sizing; Use em for Local Sizing Jump to heading

After setting the base font size at the root (html { font-size: 100%; }), set the font size for textual elements to em:

h2 {
  font-size: 2em;
}

p {
  font-size: 1em;
}

    

Then set the font-size for modules to rem:

article {
  font-size: 1.25rem;
}

aside .module {
  font-size: 0.9rem;
}

    

Now each module becomes compartmentalized and easier to style, more maintainable, and flexible.

Hide Autoplay Videos That Aren’t Muted Jump to heading

This is a great trick for a custom user stylesheet. Avoid overloading a user with sound from a video that autoplays when the page is loaded. If the sound isn’t muted, don’t show the video:

video[autoplay]:not([muted]) {
  display: none;
}

    

Once again, we’re taking advantage of using the :not() pseudo-class.

Use :root for Flexible Type Jump to heading

The type font size in a responsive layout should be able to adjust with each viewport. You can calculate the font size based on the viewport height and width using :root:

:root {
  font-size: calc(1vw + 1vh + 0.5vmin);
}

    

Now you can utilize the root em unit based on the value calculated by :root:

body {
  font: 1rem/1.6 sans-serif;
}

    

Demo

Set font-size on Form Elements for a Better Mobile Experience Jump to heading

To avoid mobile browsers (iOS Safari, et al.) from zooming in on HTML form elements when a <select> drop-down is tapped, add font-size to the selector rule:

input[type='text'],
input[type='number'],
select,
textarea {
  font-size: 16px;
}

    

:dancer:

Use Pointer Events to Control Mouse Events Jump to heading

Pointer events allow you to specify how the mouse interacts with the element it’s touching. To disable the default pointer event on a button, for instance:

.button-disabled {
  opacity: 0.5;
  pointer-events: none;
}

    

It’s that simple.

Set display: none on Line Breaks Used as Spacing Jump to heading

As Harry Roberts pointed out, this can help prevent CMS users from using extra line breaks for spacing:

br + br {
  display: none;
}

    

Use :empty to Hide Empty HTML Elements Jump to heading

If you have HTML elements that are empty, i.e., the content has yet to be set either by a CMS or dynamically injected (e.g., <p class="error-message"></p>) and it’s creating unwanted space on your layout, use the :empty pseudo-class to hide the element on the layout.

:empty {
  display: none;
}

    

Note: Keep in mind that elements with whitespace aren’t considered empty, e.g., <p class="error-message"> </p>.

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