attr function

Returns the value of an attribute of the selected element.

Below is a blockquote element which contains a character inside a data-* attribute which CSS can use (e.g. inside the ::before and ::after pseudo-element) using this function.

<blockquote data-mark='"'></blockquote>

In the following CSS block, the character is appended before and after the text inside the element:

blockquote[data-mark]::before,
blockquote[data-mark]::after {
    content: attr(data-mark);
}