Answers for "style pseudo element, style before, style after"

style pseudo element, style before, style after

<style>
div {
  width: 100px;
  height: 100px;
  position: relative;
  border: 1px solid black;
}

div:after {
  background-color: var(--my-color-var);
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
}
</style>
<div style="--my-color-var: orange;"></div>

how to use before pseudo class in css

a::before {
  content: "whatever content you want to display";
  /*css declaration*/
}