The role of content: "In css styles

In combination with the after or before pseudo class, some content is appended to the beginning or end of the element. The quotation marks of content: "Are the added content. For example, we write as follows: <div> learning and learning is nothing more than learning </div> Div: Before {content: "Zi Yue:"} Then the sub-statement is displayed: when I study it, It is also said that the "Zi Yue:" won't appear in the DOM document.

PS: Actually, this is mainly used to solve compatibility problems.

Reference: http://www.w3school.com.cn/css/pr_gen_content.asp