CSS Generated content for pseudo-elements

Method of displaying text or images before or after the given element's contents using the ::before and ::after pseudo-elements. All browsers with support also support the `attr()` notation in the `content` property.

element api: pseudo: `type` parameter: `"::after"` value

css selector: `::after`: animation and transition support

css selector: `::after`: `::after::marker` nested pseudo-elements