案例：html案例     状态：可编辑再运行    进入竖版
 运行结果　
​x
 
1
<!DOCTYPE html>
2
<html>
3
​
4
<head>
5
  <title>Creating an HTML Element</title>
6
  <script>document.createElement("myHero")</script>
7
  <style>
8
  myHero {
9
    display: block;
10
    background-color: #ddd;
11
    padding: 50px;
12
    font-size: 30px;
13
  }
14
  </style>
15
</head>
16
​
17
<body>
18
​
19
<h1>My First Heading</h1>
20
​
21
<p>My first paragraph.</p>
22
​
23
<myHero>My First Hero</myHero>
24
​
25
</body>
26
</html>