:target

css/style.css

:target {
width: 100px;
height: 30px;
background-color: #ACBEF6;
text-align: center;
line-height: 30px;
}

:target {
 width: 100px;
 height: 30px;
 background-color: #ACBEF6;
 text-align: center;
 line-height: 30px;
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<link href="css/style.css" rel="stylesheet" />
</head>
<body>
<a href="#chapter1">Chapter1</a>
<br />
<a href="#chapter2">Chapter2</a>
<br />
<a href="#chapter3">Chapter3</a>
<br />
<br />
<div>
<p id="chapter1">Chapter1</p>
<br />
<p id="chapter2">Chapter2</p>
<br />
<p id="chapter3">Chapter3</p>
</div>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<link href="css/style.css" rel="stylesheet" />
</head>
<body>
<a href="#chapter1">Chapter1</a>
<br />
<a href="#chapter2">Chapter2</a>
<br />
<a href="#chapter3">Chapter3</a>
<br />
<br />
<div>
<p id="chapter1">Chapter1</p>
<br />
<p id="chapter2">Chapter2</p>
<br />
<p id="chapter3">Chapter3</p>
</div>
</body>
</html>