Case-insensitive CSS attribute selectors

Including an `i` before the `]` in a CSS attribute selector causes the attribute value to be matched in an ASCII-case-insensitive manner. For example, `[b="xyz" i]` would match both `<a b="xyz">` and `<a b="XYZ">`.

selector list argument of :not()

Selectors Level 3 only allowed `:not()` pseudo-class to accept a single simple selector, which the element must not match any of. Thus, `:not(a, .b, [c])` or `:not(a.b[c])` did not work. Selectors Level 4 allows `:not()` to accept a list of selectors. Thus, `:not(a):not(.b):not([c])` can instead be written as `:not(a, .b, [c])` and `:not(a.b[c])` works as intended.

CSS :read-only and :read-write selectors

:read-only and :read-write pseudo-classes to match elements which are considered user-alterable

CSS 2.1 selectors

Basic CSS selectors including: `*` (universal selector), `>` (child selector), `:first-child`, `:link`, `:visited`, `:active`, `:hover`, `:focus`, `:lang()`, `+` (adjacent sibling selector), `[attr]`, `[attr="val"]`, `[attr~="val"]`, `[attr|="bar"]`, `.foo` (class selector), `#foo` (id selector)

CSS3 selectors

Advanced element selection using selectors including: `[foo^="bar"]`, `[foo$="bar"]`, `[foo*="bar"]`, `:root`, `:nth-child()`, `:nth-last-child()`, `:nth-of-type()`, `:nth-last-of-type()`, `:last-child`, `:first-of-type`, `:last-of-type`, `:only-child`, `:only-of-type`, `:empty`, `:target`, `:enabled`, `:disabled`, `:checked`, `:not()`, `~` (general sibling)

querySelector/querySelectorAll

Method of accessing DOM elements using CSS selectors

css at-rule: `@keyframes`: named timeline range keyframe selectors

css selector: `:active`

css selector: `:autofill`

css selector: `::backdrop`

css selector: `:blank`

css selector: `:buffering`

css selector: `:checked`

css selector: closed

css selector: `::cue`

css selector: `:defined`

css selector: `:disabled`

css selector: `:empty`

css selector: `:enabled`

css selector: `:focus`

css selector: `:fullscreen`

css selector: `:future`

css selector: `:host`

css selector: `:host()`

css selector: `:hover`

css selector: `:in-range`

css selector: `:invalid`

css selector: `:lang()`

css selector: `:last-child`

css selector: `:link`

css selector: `:modal`

css selector: `:muted`

css selector: `:only-child`

css selector: open

css selector: `::part`

css selector: `:past`

css selector: `:paused`

css selector: `:playing`

css selector: `:read-write`

css selector: `:required`

css selector: `:root`

css selector: `:scope`

css selector: `:seeking`

css selector: `::slotted`

css selector: `:stalled`

css selector: `:target`

css selector: `:user-valid`

css selector: `:valid`

css selector: `:visited`

css selector: `:where()`