Simple A/B test

HTML

<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        #call {
            background-color: rgb(0, 0, 200);
            border: none;
            color: white;
            padding: 15px 32px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
            margin-bottom: 20px;
        }
        
        #wrapper {
            height: 270px;
            background-image: url(https://ww2-secure.justanswer.com/static/img/sip-prominent-v2/Lawyer.jpg);
            background-size: contain;
            background-repeat: no-repeat;
            margin-bottom: 20px;
        }
    </style>
</head>

<body>
    <script type="text/javascript">
        function downloadJSAtOnload() {
            var element = document.createElement("script");
            element.src = "https://ww2-secure.justanswer.com/static/ab-test/client_side_ab.js?rand=" + Date.now();
            document.body.appendChild(element);
        }

        if (window.addEventListener)
            window.addEventListener("load", downloadJSAtOnload, false);
        else if (window.attachEvent)
            window.attachEvent("onload", downloadJSAtOnload);
        else window.onload = downloadJSAtOnload;
    </script>
    <p id="variation">Original Page (A)</p>
    <div id="wrapper"></div>
    <button id="call">Call now!</button>
    <div>
        <a href="#" onclick="clearCookie()">Clear cookie</a>
    </div>
</body>

</html>