The s identifier in a CSS attribute selector matches attribute values case-sensitively in document languages like HTML where attribute values are case-insensitive.

The :has-slotted CSS pseudo-class matches <slot> elements where the fallback content is not shown. The pseudo-class matches any slotted content, including white space, text nodes, or elements.

The ::spelling-error and ::grammar-error CSS pseudo-elements match text that is highlighted as misspelled and grammatically incorrect, respectively.

The text-decoration CSS property in a ::selection rule sets the underline and other text decoration styles on the text a user has highlighted.

The :past and :future CSS pseudo-classes match prior or upcoming text track cues during media playback.

The :host-context() CSS pseudo-class selects the containing element of the shadow tree in which it is used if that element or an ancestor matches the provided selector.

The ::selection CSS pseudo-element selects text a user has highlighted.

The :first, :left, and :right pseudo-classes select pages based on their position in sequence after pagination.

The :heading and :heading() CSS pseudo-classes match headings of varying levels. The :heading pseudo-class matches any heading (<h1> through <h6>). The :heading() selector matches any of the given levels. For example, :heading(1, 2) matches headings level 1 and 2.

The :target-within CSS pseudo-class matches the element with an ID matching the URL fragment and its ancestors.