StyleTest

HTML

<link id="style" href="//l24.su/css/app.css" rel="stylesheet">
<div class="">
<div class="box">
<a onclick="setStyle('//l24.su/css/app.css')" href="#">Style 1</a>
<a onclick="setStyle('//l24.su/css/randomfollowers.css')" href="#">Style 2</a>
</div>
</div>



<script>
function setStyle(css) {
  document.querySelector('link#style').href = css;
}
</script>