W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body {font-family: Arial;}

/* Style the tab */
.tab {
  overflow: hidden;
  border: 1px solid #ccc;
  background-color: #f1f1f1;
}

/* Style the buttons inside the tab */
.tab button {
  background-color: inherit;
  float: left;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 14px 16px;
  transition: 0.3s;
  font-size: 17px;
}

/* Change background color of buttons on hover */
.tab button:hover {
  background-color: #ddd;
}

/* Create an active/current tablink class */
.tab button.active {
  background-color: #ccc;
}

/* Style the tab content */
.tabcontent {
  display: none;
  padding: 6px 12px;
  border: 1px solid #ccc;
  border-top: none;
}

/* Style the close button */
.topright {
  float: right;
  cursor: pointer;
  font-size: 28px;
}

.topright:hover {color: red;}
</style>
</head>
<body>

<h2>Tabs</h2>
<p>Click on the x button in the top right corner to close the current tab:</p>

<div class="tab">
  <button class="tablinks" onclick="openCity(event, 'London')" id="defaultOpen">London</button>
  <button class="tablinks" onclick="openCity(event, 'Paris')">Paris</button>
  <button class="tablinks" onclick="openCity(event, 'Tokyo')">Tokyo</button>
</div>

<div id="London" class="tabcontent">
  <span onclick="this.parentElement.style.display='none'" class="topright">&times</span>
  <h3>London</h3>
  <p>London is the capital city of England.</p>
</div>

<div id="Paris" class="tabcontent">
  <span onclick="this.parentElement.style.display='none'" class="topright">&times</span>
  <h3>Paris</h3>
  <p>Paris is the capital of France.</p> 
</div>

<div id="Tokyo" class="tabcontent">
  <span onclick="this.parentElement.style.display='none'" class="topright">&times</span>
  <h3>Tokyo</h3>
  <p>Tokyo is the capital of Japan.</p>
</div>

// Get the element with id="defaultOpen" and click on it
document.getElementById("defaultOpen").click();
</script>
   
</body>
</html>