popup.html

<html> 
    <head> <!--specifies metadata  -->
        <title> Lecture Download </title>
        <style>  
          /* specifies to the runtime environment that this is css*/      
        button {
            background-color: #4CAF50;
            border: none;
            color: white;
            padding: 15px 32px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
            margin: 4px 2px;
            cursor: pointer;
        }
        </style>
    </head>
    <body> 
        <!-- This actually adds the button element -->
        <button id="mybutton"> Download Lectures! </button>

        <!-- The javascript script that is called when the 
            button is  pressed -->
        <script src="src/popup.js"></script>
        
    </body>
</html>