Even if all browsers are fault-tolerant, HTML tags should be closed to prevent any unexpected behavior.
Noncompliant code example
<html>
<head>
<title>Test Page <!-- Noncompliant; title not closed -->
<!-- Noncompliant; head not closed -->
<body>
<em>Emphasized Text <!-- Noncompliant; em not closed -->
<!-- Noncompliant; body not closed -->
</html>
Compliant solution
<html>
<head>
<title>Test Page</title>
</head>
<body>
<em>Emphasized Text</em>
</body>
</html>
