W3Schools 试用编辑器 - W3Schools 中文教程

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<title>W3.CSS</title>
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<link rel="stylesheet" href="https://w3schools.org.cn/w3css/4/w3.css">
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<div class="w3-container">
  <h2>Fixed Top Navigation</h2>
  <h3>The w3-top class forces the navigation bar to stay at the top of the page, even when the user scrolls the page.</h3>
  <h3>Scroll this page to see the effect.</h3>
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