JSFiddle - React, Tailwind, and code Playground

HTML

<div id='wrap'>
  <div id='posts'></div>

  <div id='sidebar'>
    <div class='widget'></div>
    <div class='widget'></div>
  </div>
</div>

CSS

*{margin:0;padding:0;-webkit-box-sizing:border-box;-moz-box-sizing:border-box;-ms-box-sizing:border-box;-o-box-sizing:border-box;box-sizing:border-box;}

#wrap{width:90%;margin:30px auto;background:#DDD;padding:20px;overflow:hidden;}
#posts{float:left;width:68%;height:2000px;background:#333;}
#sidebar{float:right;width:30%;background:#CD0000;padding:10px;}
#sidebar .widget{width:100%;height:300px;background:#111;margin:0 0 20px;}
#sidebar .widget:last-of-type{margin-bottom:0}