selector element

css/style.css

.a {
font-size: 36px;
}
.a p{
color: #00F;
}

.a {
 font-size: 36px;
}

.a p{
 color: #00F;
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<link href="css/style.css" rel="stylesheet" />
</head>
<body>
<div class="a">
<p>Hello World!</p>
<h4>To be or not to be?</h4>
<p>Привет Мир!</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>
<div class="a">
<p>Hello World!</p>
<h4>To be or not to be?</h4>
<p>Привет Мир!</p>
</div>
</body>
</html>