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   <!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="head-1">
    Header
  </div>
  <div class="menu">
    <div class="menu-layout">
     Menu
    </div>
  </div>
  <div class="promo">
    <div class="promo-1">
      Promo 1
    </div>
    <div class="promo-2">
     Promo 2
    </div>
  </div>
</div>
<div class="content"> 
  <div class="colons">
    <div class="left">
      Left
    </div>
    <div class="main">
      Main
    </div>
    <div class="right">
      Right
    </div>
  </div>
</div>
<div class="footer">
  <div class="footer-1">
  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;
        }
        .header{
          background-color:#34495e;
          padding-top:10px;
          padding-bottom:10px;
        }

        .head-1{
          width:340px;
          height:25px;
          margin:auto;
          padding:5px;
          background-color:#c0392b;
        }
        .menu{
          background-color:#3498db;
          height:35px;
          margin-top:10px;
          margin-bottom:10px;
        }
        .menu-layout{
          width:340px;
          margin:auto;
          padding:5px;
        }
        .promo{
          width:350px;
          margin: auto;
          height: 60px;
          
        }
        .promo-1{
          float:left;
          width:160px;
          height:50px;
          padding:5px;
          margin-right:10px;
          background-color:#c0392b;
        }
        .promo-2{
          float:right;
          width:160px;
          height:50px;
          padding:5px;
          background-color:#c0392b;
        }
        .content{
          
          padding-top:10px;
          padding-bottom:10px;
        }
        .colons{
          
          width:350px;
          margin: auto;
          height: 110px;
        }
        .left{
          float:left;
          width:60px;
          height:100px;
          padding:5px;
          margin-right:10px;
          background-color:#3498db;
        }
        .main{
          float:left;
          width:180px;
          height:100px;
          padding:5px;
          margin-right:10px;
          background-color:#3498db;
        }
        .right{
          float:right;
          width:60px;
          height:100px;
          padding:5px;
          background-color:#3498db;
        }
        .footer{
          background-color:#34495e;
          
          padding-bottom:10px;
        }
        .footer-1{
          width:340px;
          height:25px;
          margin:auto;
          padding:5px;
        }