<!DOCTYPE html>
<html>
<head>
</head>
<body>
<p>Click the button to create a STYLE element, and place it in the head section.</p>
<button onclick="myFunction()">Try it</button>
<p>The created style element contains css declarations that will change the font properties of this document.</p>
<script>
function myFunction() {
var x = document.createElement("STYLE");
var t = document.createTextNode("body {font: 20px verdana;}");
x.appendChild(t);
document.head.appendChild(x);
}
</script>
</body>
</html>