::before and ::afterThe ::before and ::after CSS pseudo-elements select inline boxes preceding and following an element. They are often used with the content property to generate cosmetic content.widely2015-07-292018-01-29https://drafts.csswg.org/css-pseudo-4/#generated-contentcss-gencontenthttps://developer.mozilla.org/docs/Web/CSS/Reference/Selectors/::aftercss.selectors.aftercss.selectors.after.animation_and_transition_supportcss.selectors.beforecss.selectors.before.animation_and_transition_supporthttps://nowyoucanuse.com/features--before-after.html