JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
  <body>
    <section id="left-side"></section>
    <section id="right-side">
      <div id="floater">
        <p>
          Helvetica fap jean shorts gentrify. Polaroid mustache twee photo booth lo-fi. Synth master cleanse before they sold out brunch lomo kale chips umami mustache. Keytar kale chips chillwave, post-ironic umami dreamcatcher vinyl swag gastropub. Beard pop-up polaroid, Austin high life farm-to-table small batch photo booth dreamcatcher tattooed vegan irony. Fap american apparel locavore pinterest messenger bag mlkshk 3 wolf moon. Iphone odd future jean shorts, dreamcatcher sriracha yr quinoa DIY raw denim art party authentic tofu.
        </p>
        <p>
          Vinyl pitchfork viral pour-over marfa, squid cliche aesthetic put a bird on it truffaut mumblecore post-ironic sartorial. Swag ethical ethnic PBR, helvetica selvage seitan mustache authentic bushwick aesthetic. Dreamcatcher gastropub lo-fi keytar, banksy vegan readymade wolf keffiyeh mustache food truck quinoa. Gentrify farm-to-table echo park brunch, skateboard you probably haven't heard of them pour-over brooklyn banksy cred. Direct trade swag hella kale chips small batch. Vice raw denim whatever VHS, salvia next level kale chips keytar high life 3 wolf moon semiotics freegan. Pour-over artisan shoreditch scenester fanny pack, mustache typewriter terry richardson helvetica biodiesel.
        </p>
      </div>
    </section>
  </body>
</html>

CSS

html, body  { margin:0px;padding:0px;height:100%;width:100%; }
      #left-side  { float:left;background-color:#E5EBF2;width:25%;border-right: 1px solid #B4B4B4;height:100%; }
      #right-side { float:left;position:relative;height:100%;width:70%; }
      #floater    { background-color:lightgray;position:absolute;padding:5px;width:365px;top:20px;left:-15px;-moz-box-shadow: 0 4px 8px rgba(0,0,0,0.6);-webkit-box-shadow: 0 4px 8px rgba(0,0,0,0.6);-o-box-shadow: 0 4px 8px rgba(0,0,0,0.6);box-shadow: 0 4px 8px rgba(0,0,0,0.6); }
      /*the `magic`*/
      #floater    { overflow-y:auto;height:auto;max-height:90%; }