:lt(index)

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
</head>
<body>
<div id="main">
<p>Number 0</p>
<p>Number 1</p>
<p>Number 2</p>
<p>Number 3</p>
<p>Number 4</p>
<p>Number 5</p>
<p>Number 6</p>
<p>Number 7</p>
</div>
<script>
$(document).ready(function() {
$('#main>p:lt(5)').css({'color': '#F00', 'font-size': '20px'});
});
</script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
</head>
<body>
<div id="main">
<p>Number 0</p>
<p>Number 1</p>
<p>Number 2</p>
<p>Number 3</p>
<p>Number 4</p>
<p>Number 5</p>
<p>Number 6</p>
<p>Number 7</p>
</div>
<script>
$(document).ready(function() {
$('#main>p:lt(5)').css({'color': '#F00', 'font-size': '20px'});
});
</script>
</body>
</html>