W3Schools Tryit Editor

<!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/4/w3.css">
<body class="w3-container w3-auto">

<h2>W3.CSS Alerts</h2>
<p>The w3-panel class is used to display alerts:</p>

<div class="w3-panel w3-pale-red w3-border">
  <h3>Danger!</h3>
  <p>Red often indicates a dangerous or negative situation.</p>
</div>

<div class="w3-panel w3-pale-yellow w3-border">
  <h3>Warning!</h3>
  <p>Yellow or orange often indicates a warning that might need attention.</p>
</div>

<div class="w3-panel w3-pale-green w3-border">
  <h3>Success!</h3>
  <p>Green often indicates something successful or positive.</p>
</div>

<div class="w3-panel w3-pale-blue w3-border">
  <h3>Information!</h3>
  <p>Blue often indicates a neutral informative change or action.</p>
</div>

<div class="w3-panel w3-red">
  <h3>Danger!</h3>
  <p>Red often indicates a dangerous or negative situation.</p>
</div>

<div class="w3-panel w3-yellow">
  <h3>Warning!</h3>
  <p>Yellow or orange often indicates a warning that might need attention.</p>
</div>

<div class="w3-panel w3-green">
  <h3>Success!</h3>
  <p>Green often indicates something successful or positive.</p>
</div>

<div class="w3-panel w3-blue w3">
  <h3>Information!</h3>
  <p>Blue often indicates a neutral informative change or action.</p>
</div>

</body>
</html>