Opt-Out Responsive V2

<!doctype html>
<html lang="en" class="no-js">
<head>
  <meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0">
<style type="text/css">
.content { margin: 0 auto; }
.responsive .content{ background:yellow; width: 70% }
.responsive .fixed-width-link { display: block; }
.responsive .responsive-link { display: none; }
.fixed-width .content { background:red; width: 600px; }
.fixed-width .fixed-width-link { display: none; }
.fixed-width .responsive-link { display: block; }
</style>
</head>
<body class="responsive">
<script type="text/javascript">
(function(doc, classToAdd){
   doc.className = (doc.className).replace("no-js", classToAdd);
})(document.documentElement, "js");
function FixedWidth() {
    (function(body, classToAdd) {
        body.className = (body.className).replace("responsive", classToAdd);
    })(document.body, "fixed-width");
    viewport = document.querySelector("meta[name=viewport]");
    viewport.setAttribute('content', 'width=device-width, user-scalable=yes, initial-scale=1.0');
}
function Responsive() {
    (function(body, classToAdd) {
        body.className = (body.className).replace("fixed-width", classToAdd);
    })(document.body, "responsive");
    viewport = document.querySelector("meta[name=viewport]");
    viewport.setAttribute('content', 'width=device-width, user-scalable=no, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0');
}
window.onload = FixedWidth;
window.onload = Responsive;
</script>
<div class="content">
    <h1 class="fixed-width-link">Responsive</h1>
    <h1 class="responsive-link">Fixed Width</h1>
    <a href="#" onclick="return FixedWidth()" class="fixed-width-link">Fixed Width</a>
    <a href="#" onclick="return Responsive()" class="responsive-link">Reponsive</a>
</div>
</body>
</html>