SOURCE

<div>
  Can I haz semi-transparent borders? Pretty please?
</div>

/**
 * Translucent borders
 */

body {
  background: url('http://csssecrets.io/images/stone-art.jpg');
}

div {
  border: 10px solid hsla(0, 0%, 100%, .5);
  background: white;
  background-clip: padding-box;
  
  /* styling */
  max-width: 20em;
  padding: 2em;
  margin: 2em auto 0;
  font: 100%/1.5 sans-serif;
}