<!DOCTYPE html>
<html lang="en-US">
<head>
<style>
input:indeterminate{
box-shadow: 0 0 3px 5px black;
}
</style>
</head>
<body>
<h1>CSS :checked Selector</h1>
<input type="checkbox"> Click on the checkbox
<script>
var x = document.getElementsByTagName("input")[0];
x.indeterminate = true;
</script>
<p><strong>Note</strong>: Here checkbox is set to indeterminate state using javascript.</p> </body>
</html>