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<!DOCTYPE html> <meta charset="utf-8"> <link href="/static/next/css/tryit.css?v=2017082407" rel="stylesheet"/> <script src="https://cdn.staticfile.org/jquery/2.2.4/jquery.min.js"></script> <script> $(document).ready(function(){ $("div p:first-child").css("background-color","yellow"); }); </script> <p>The first paragraph in body.</p> <div style="border:1px solid;"> <p>The first paragraph in div.</p> <p>The last paragraph in div.</p> </div><br> <div style="border:1px solid;"> <p>The first paragraph in another div.</p> <p>The last paragraph in another div.</p> </div> <p>The last paragraph in body.</p> <footer>简单教程，简单编程<br/>Copyright © 简单教程 www.twle.cn</footer>
运行结果：