JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content_center">
    <div id="content_wrap" class="clearfix rounded border dark">
        <div id="content_left">left</div>
        <div id="content_right">right</div>
    </div>
</div>

CSS

*{
    margin:0;padding:0;
}

body{
    background-color: #3F3965;
    font-family: Verdana, Geneva, sans-serif;
    color:#000;
}

.content_center {
    width: 800px;
    margin: 0 auto;
}

#content_wrap{
    padding: 0;
    width: 100%;
    background-color: #FFF;
}

#content_left{
    width: 180px;
    float: left;
}

#content_right {
    width: 620px;
    float: left;
}

.rounded {
  -moz-border-radius: 10px; /* Firefox */
  -webkit-border-radius: 10px; /* Safari, Chrome */
  border-radius: 10px; /* CSS3 */
  behavior: url(border-radius.htc);
}

.border {
    border: solid 2px;
}

.light {
    border-color:#999;
}

.dark {
    border-color:#666;
}

.clr {
    clear:both;
}

.clearfix:after {
    content: ".";
    display: block;
    clear: both;
    visibility: hidden;
    line-height: 0;
    height: 0;
}

.clearfix {
    display:inline-block;
}

html[xmlns] .clearfix {
    display: block;
}

* html .clearfix {
    height: 1%;
}