<!DOCTYPE html>
<html lang="en-US">
<head>
<title>text-decoration alignment</title>
<meta charset=UTF-8>
<style>

p, span { text-decoration: underline }
span { vertical-align: 8px }
p > span { color: fuchsia }
p > span > span { color: aqua }

em { font-style: normal; font-size: 5em }

</style>
</head>
<body>

<p>x<span>x<span>x</span></span></p>

</body>
</html>