MDN’s new design is in Beta! A sneak peek: https://blog.mozilla.org/opendesign/mdns-new-design-beta/
非標準
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
:-moz-alt-text は読み込まれなかった画像のための代替テキストを提供する要素にマッチします。
このセレクタは主にテーマ開発者によって使用されるものです。
:active:any [Translate]:checked:dir:disabled:empty:enabled:first:first-child:first-of-type:fullscreen:focus:hover:indeterminate:invalid:lang:last-child:last-of-type:left:link:not():nth-child:nth-last-child:nth-last-of-type:nth-of-type:only-child:only-of-type:optional:out-of-range [Translate]:read-write:required:right:root:scope [Translate]:target:valid