<!DOCTYPE html>
<html>
<head>
<style>
body {
    background-color: yellow;
    color: red;
    font-size: 15px;
}

</style>
</head>
<body>

<p>Click the button to display the style properties of this document.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementsByTagName("STYLE")[0];
    document.getElementById("demo").innerHTML = x.innerHTML;
}
</script>

</body>
</html>