ready()

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>
<p id="p0"></p>
<script>
$(document).ready(function() {
$('#p0').text('Hello World!');
});
</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>
<p id="p0"></p>
<script>
$(document).ready(function() {
$('#p0').text('Hello World!');
});
</script>
</body>
</html>