<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("div p").first().css("background-color","yellow");
});
</script>
</head>
<body>
<h1>Welcome to My Homepage</h1>
<div>
<p>This is a paragraph in a div.</p>
</div>
<div>
<p>This is a paragraph in another div.</p>
</div>
<p>This is also a paragraph.</p>
</body>
</html>