Pseudo elements allow us to target elements that are not explicitly set in the DOM. Using ::before ::after we can actually create and manipulate elements in the DOM that do not impact the content. While ::first-letter ::first-line ::selection ::placeholder allow us to target elements that do not have a specific DOM element.
About ‘blockquote‘:
blockquote { ?quotes: "“" "”" "‘" "’";}blockquote::before { ?content: open-quote;}blockquote::after { ?content: close-quote;}About ::first-line, ::first-letter:
p::first-line { ?color: green;}p::first-letter { ?font-size: 2em; ?float: left; ?line-height: 1.7em; ?padding: 0 .3em; ?font-weight: bold;}[CSS3] Target HTML Elements not Explicitly set in the DOM with CSS Pseudo Elements
原文地址：https://www.cnblogs.com/Answer1215/p/10068269.html