devdocs/assets/stylesheets/components/_fail.scss

._fail { // Don't use CSS variables, in case the browser doesn't support them.
  display: block;
  position: relative;
  top: 1.5rem;
  width: 24rem;
  max-width: 90%;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  background: #eaefef;
  border-radius: 5px;
  @extend %border-box;

  &:after { // margin
    content: '';
    position: relative;
    top: 3rem;
    float: left;
    width: 1px;
    height: 1px;
  }
}

._fail-title {
  margin: 0 0 1rem;
  font-size: 1rem;
  font-weight: bold;
}

._fail-text, ._fail-list {
  margin: 0 0 1rem;
  font-size: .875rem;
}

._fail-text:last-child { margin: 0; }