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<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.com/w3css/5/w3.css">
<body>

<div class="w3-container">
  <h2>Active Tabs</h2>
  <p>To highlight the current tab/page the user is on, add a color class, and use JavaScript to update the active link.</p>

<div class="w3-bar w3-black">
    <button class="w3-bar-item w3-button tablink w3-red" onclick="openCity(event,'London')">London</button>
    <button class="w3-bar-item w3-button tablink" onclick="openCity(event,'Paris')">Paris</button>
    <button class="w3-bar-item w3-button tablink" onclick="openCity(event,'Tokyo')">Tokyo</button>
  </div>
  
  <div id="London" class="w3-container w3-border city">
    <h2>London</h2>
    <p>London is the capital city of England.</p>
  </div>

<div id="Paris" class="w3-container w3-border city" style="display:none">
    <h2>Paris</h2>
    <p>Paris is the capital of France.</p> 
  </div>

<div id="Tokyo" class="w3-container w3-border city" style="display:none">
    <h2>Tokyo</h2>
    <p>Tokyo is the capital of Japan.</p>
  </div>
</div>

</body>
</html>

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<!DOCTYPE html><html><title>W3.CSS</title><meta name="viewport" content="width=device-width, initial-scale=1"><link rel="stylesheet" href="https://www.w3schools.com/w3css/5/w3.css"><body>​<div class="w3-container">  <h2>Active Tabs</h2>  <p>To highlight the current tab/page the user is on, add a color class, and use JavaScript to update the active link.</p>​  <div class="w3-bar w3-black">    <button class="w3-bar-item w3-button tablink w3-red" onclick="openCity(event,'London')">London</button>    <button class="w3-bar-item w3-button tablink" onclick="openCity(event,'Paris')">Paris</button>    <button class="w3-bar-item w3-button tablink" onclick="openCity(event,'Tokyo')">Tokyo</button>  </div>    <div id="London" class="w3-container w3-border city">    <h2>London</h2>    <p>London is the capital city of England.</p>  </div>​  <div id="Paris" class="w3-container w3-border city" style="display:none">    <h2>Paris</h2>    <p>Paris is the capital of France.</p>   </div>​  <div id="Tokyo" class="w3-container w3-border city" style="display:none">    <h2>Tokyo</h2>    <p>Tokyo is the capital of Japan.</p>  </div></div>​<script>function openCity(evt, cityName) {  var i, x, tablinks;  x = document.getElementsByClassName("city");  for (i = 0; i < x.length; i++) {    x[i].style.display = "none";  }  tablinks = document.getElementsByClassName("tablink");