<div class="alert-primary">Primary alert</div><br>
    <div class="alert-secondary">Secondary alert</div><br>
    <div class="alert-success">Success alert</div><br>
    <div class="alert-warning">Warning alert</div><br>
    <div class="alert-info">Info alert</div><br>
    <div class="alert-danger">Danger alert</div><br>

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.