<link rel="help" href="https://www.w3.org/TR/css-ui-4/#outline-offset">

<link rel="match" href="negative-outline-offset-ref.html">

div {

outline: 1px solid red;

outline-offset: -10em;

border: 2px solid black;

padding: 5px;

font-size: 16px;

}

<p>PASS if there is a thin red line in the middle of the box.</p>