Get your own website Result Size: 625 x 565
x
 
<!DOCTYPE html>
<html>
<head>
<style> 
div.container {
  width: 100%;
  border: 2px solid black;
}
div.box {
  box-sizing: border-box;
  width: 50%;
  border: 5px solid red;
  float: left;
}
</style>
</head>
<body>
<div class="container">
  <div class="box">This div occupies the left half</div>
  <div class="box">This div occupies the right half</div>
  <div style="clear:both;"></div>
</div>
</body>
</html>