Use a generic close icon for dismissing content like modals and alerts. Be sure to include text for screen readers, as we've done with aria-label
.
<button type="button" class="close" aria-label="Close">
<span aria-hidden="true">×</span>
</button>
Use text color utility overrides against alternate background colors for greater visibility:
<button type="button" class="close text-inverse" aria-label="Close">
<span aria-hidden="true">×</span>
</button>