JSFiddle - React, Tailwind, and code Playground
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>test</title>
</head>
<body>
<div id="bases-container">
<div id="top-2-divs-container">
<div id="top-left-div" class="top-2-divs base-container">
</div>
<div id="top-right-div" class="top-2-divs base-container">
</div>
</div>
<div id="bot" class="base-container">
</div>
</div>
</body>
</html>
CSS
*{font-family:verdana;font-size:12px;margin:0;padding:0;}
body{background:#ddd;}
input::-moz-focus-inner{border:0;padding:0;}
a:link,a:visited,a:active{outline:0;text-decoration:none;}
#bases-container{margin:30px auto;width:750px;}
#top-base{width:748px;height:416px;}
.base-container{background:#fff;border:1px solid #a8a8a8;}
#top-2-divs-container{
width:750px;
height:191px;
margin-bottom:4px;
}
.top-2-divs{
width:370px;
height:189px;
}
#top-left-div{
float:left;
}
#top-right-div{
float:right;
}
#bot{
width:748px;height:220px;
}