wagtail/client/scss/components/_preview-error.scss

.preview-error {
  @apply w-bg-surface-page;
  position: absolute;
  inset-inline-start: 0;
  width: 100%;
  display: grid;
  min-height: 100vh;
  align-content: center;
  text-align: center;

  &__header {
    margin-bottom: 0.5rem;
  }

  &__title {
    @apply w-h4 w-text-text-context;
  }

  &__details {
    @apply w-help-text;
  }
}