The @function CSS at-rule defines a custom function that takes CSS values or custom properties as arguments, and returns a CSS value. It can be based on conditional logic such as by using the @media at-rule.

The @mixin and @apply CSS at-rules define reusable style declaration fragments and apply them inside rules, optionally passing arguments.

The rel="alternate stylesheet" attribute for the <link> HTML element offers an alternative style option to users.

The cursor CSS property styles the pointer, allowing you to provide hints to the user on how to interact with the hovered element.

The accent-color CSS property sets a color for checkboxes, radio buttons, and other form controls.

The at-rule() function, when used with @supports, checks if a CSS at-rule is supported. For example @supports at-rule(@starting-style) checks if the @starting-style at-rule is supported.

The attr() CSS function, in the context of any property, returns the value of an attribute of an HTML element, with the option to return it as a specific type or unit. You can set a default value for missing or invalid attributes.

The calc-size() CSS function computes mathematical expressions that include height and width keyword values, for example calc-size(fit-content, size / 2). Not to be confused with the calc() CSS function, which cannot use keyword values.

You can animate elements between display: none and any other display value or animate between content-visibility: hidden and any other content-visibility value. This also applies to transitions.

The display: contents CSS declaration sets an element to display only its contents, not itself.

The display: ruby CSS declaration renders an element with the box layout of a <ruby> HTML element. Child elements may use equivalents to <ruby> internal elements such as display: ruby-base for <rb>.

The dynamic-range-limit CSS property controls the peak luminance of high dynamic range content. You can use this to coordinate the apparent brightness of HDR and SDR content.

The filter() CSS function applies one or more graphic effects to a CSS image, such as a background image. You can use functions, such as blur() and drop-shadow(), alone or combined to produce different effects. For instance, background: filter(url(image.png), blur(2px)).

The glyph-orientation-vertical CSS property sets the orientation of glyphs in text rendered in a vertical writing mode.

The if() CSS function is an inline conditional value that returns a value based on a set of conditions.

The ime-mode CSS property sets the state of the input method editor for text fields.

The initial-letter CSS property sets the number of lines the first letter of an element occupies. You can use the property to make a raised capital or drop cap.

The line-clamp CSS property limits the text in a block container to a certain number of lines. The prefixed -webkit-line-clamp is widely supported but only works with -webkit-box-orient: vertical in combination with display: -webkit-box or display: -webkit-inline-box.

The margin-trim CSS property removes the margins of child elements when they meet the edges of the container.

The object-view-box CSS property crops and zooms to an inset area of an image.

The overflow-clip-margin CSS property sets how far overflow content may appear outside the bounds of an element before it's clipped by effects such as overflow: clip.

The overflow: overlay CSS declaration is an alias to overflow: auto. Historically, it caused non-standard behavior, allowing scrollbars to overlay content without taking up layout space.

The overlay CSS property, used as an allow-discrete CSS transition, prevents a top layer element, such as a popover or a <dialog>, from being removed from the top layer before it has finished animating. You can't set the value of the overlay property; only use it as transition property.

The paint() CSS function creates a custom image, drawn using a paint worklet, for an element's background or border.