框架，可以在同一个浏览器窗口中显示不止一个页面。
<!DOCType html>
<html>
<head>
<meta charset="utf-8">
<title>框架</title>
</head>
<body>
<iframe src="test1.html" name="iframe_a" width="800" height="600"></iframe>
<p><a href="test2.html" target="iframe_a" rel="noopener">BAIDU.COM</a></p>
</body>
</html>><!DOCType html>
<html>
<head>
<title>test1页面</title>
</head>
<body>
<img src="pictures/girl.jpeg">
</body>
</html>><!DOCType html>
<html>
<head>
<title>test2页面</title>
</head>
<body>
<img src="pictures/dragonCat.jpeg">
</body>
</html>>
