JSFiddle - React, Tailwind, and code Playground

HTML

<div class="la-alert-header">
	<span>Alert</span>
	<div class="la-alert-close-ico">
		
	</div>
</div>

CSS

body{
	background: silver;
}.la-alert-close-ico {
  position: absolute;
  right: 0;
  top: 0;
  width: 13px;
  height: 13px;
  opacity: 0.3;
	border: 1px solid white;
}
.la-alert-close-ico:hover {
  opacity: 1;
}
.la-alert-close-ico:before, .la-alert-close-ico:after {
  position: absolute;
  left: 5px;
  content: ' ';
  height: 13px;
  width: 2px;
  background-color: white;
}
.la-alert-close-ico:before {
  transform: rotate(45deg);
}
.la-alert-close-ico:after {
  transform: rotate(-45deg);
}