使用font-size-adjus t属性可以在发生字体回退时保留可读性。您可以尝试运行以下代码来实现font-size-adjust属性：
<!DOCTYPE html>
<html>
<head>
<style>
#demo {
font-size-adjust: 0.90;
}
</style>
</head>
<body>
<h2>Heading Two</h2>
<h2>With font-size-adjust property:</h2>
<div class = "demo">
This is demo text.
</div>
<h2>Without font-size-adjust property:</h2>
<div>This is demo text.</div>
</body>
</html>