27/32 99% Где ошибка?


#1
<!DOCTYPE html>
<html lang="ru">
  <head>
    <title>Испытание: строим сетку</title>
    <meta charset="utf-8">
    <link rel="stylesheet" href="style.css">
  </head>
  <body>
    <div class="header">
      <div class="helper">
        <div class="hcont">Header</div>
      </div>
    </div>
    <div class="menu">
      <div class="mcont">Menu</div>
    </div>
    <div class="promo">
      <div class="helper center">
        <div class="pcont1">Promo 1</div>
        <div class="pcont2">Promo 2</div>
      </div>
    </div>
    <div class="storon">
      <div class="center">
        <div class="scont">Left</div>
        <div class="scont">Main</div>
        <div class="scont">Right</div>
      </div>
    </div>
    <div class="foot">
      <div class="fcont">Footer</div>
    </div>
  </body>
</html>

Css

html,
body {
  margin: 0;
  padding: 0;
}

body {
  width: 450px;
  height: 335px;

  font-size: 10px;
  font-family: "Arial", sans-serif;
  color: white;
}
.helper {
  padding: 10px;
}
.center {
  margin: 0;
  width: 450px;
}
.center::after {
  content:"";
  display: table;
  clear: both;
}
.header {
  background-color:#34495e;
  height: 55px;
}
.hcont {
  background-color: #c0392b;
  min-height: 25px;
  margin: 0 40px;
  padding: 5px;
}
.menu {
  background-color: #3498db;
  height: 35px;
}
.mcont {
  padding: 5px 55px;
}
.promo {
  background-color:#34495e;
  height: 80px;
}
.pcont1 {
  float: left;
  background-color: #c0392d;
  min-height: 50px;
  margin-left: 40px;
  width: 160px;
  margin-right: 10px;
  padding: 5px
}
.pcont2 {
  float: left;
  background-color: #c0392d;
  min-height: 50px;
  margin-right: 40px;
  width: 160px;
  padding: 5px
}
.storon {
  height 150px;
}
.scont {
  height: 100px;
  background-color: #3498db;
  float: left;
  width: 60px;
  margin: 10px 5px 10px 5px;
  padding: 5px;
}
.scont:last-child {
  float: right;
  margin-right: 50px;
}
.scont:first-child {
  float: left;
  margin-left: 50px;
}
.scont:nth-child(2) {
  float: left;
  width: 180px;
}
.foot {
  height: 35px;
  background-color: #34495e;
  padding: 5px 55px;
}

/*
  Используемые цвета:
  #34495e – мокрый асфальт
  #c0392b – красный
  #3498db – синий
*/

Где ошибка?

Скриншоты