<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Welcome!</title>
</head>
<body>
NG パターン
<a href="javascript:alert('hello');">
</a><p><a href="javascript:alert('hello');">aaa</a></p>
<p>aaa</p>
<a href="javascript:alert('hello');">
</a><section><a href="javascript:alert('hello');">
</a><p><a href="javascript:alert('hello');">aaa</a></p>
<p>aaa</p>
</section>
OK パターン
<a href="javascript:alert('hello');">
<div>
<p>aaa</p>
<p>aaa</p>
</div>
</a>
<a href="javascript:alert('hello');">
<div>aaa</div>
<div>aaa</div>
</a>
<a href="javascript:alert('hello');">
<blockquote>
<p>aaa</p>
<p>aaa</p>
</blockquote>
</a>
<a href="javascript:alert('hello');">
<form>
<p>aaa</p>
<p>aaa</p>
</form>
</a>
</body>
</html>