foo
sample3.html 
<!DOCTYPE HTML>
<html lang="ja">
  <head>
    <meta charset="UTF-8">
    <title>test</title>
  </head>
  <body>
    <div id="foo">foo</div>
    <div><iframe src="iframe3_1.html"></iframe></div>
    <div><iframe name="bar" src="iframe3_2.html"></iframe></div>
  </body>
</html>
iframe3_1.html 
<!DOCTYPE HTML>
<html lang="ja">
  <head>
    <meta charset="UTF-8">
    <title>iframe</title>
  </head>
  <body>
    <div>
      <a href="iframe2.html">iframe2.htmlに移動（target属性なし）</a><br />
      <a href="iframe2.html" target="_top">iframe2.htmlへ移動（target属性に「_top」指定）</a><br />
      <a href="iframe2.html" target="_blank">iframe2.htmlへ移動（target属性に「_blank」指定）</a>
      <a href="iframe2.html" target="bar">iframe2.htmlへ移動（target属性に「bar」指定）</a>
    </div>
  </body>
</html>
iframe3_2.html 
<!DOCTYPE HTML>
<html lang="ja">
  <head>
    <meta charset="UTF-8">
    <title>iframe</title>
    <style>
    body { margin: 10px; }
    </style>
  </head>
  <body>
    <div>このインラインフレームのname属性は"bar"です。</div>
  </body>
</html>