open_in_new content_copy 
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>Document</title>
</head>
<body>
    <div class="page">
        <div class="menu">MENU</div>
            <div class="clearfix">
                <div class="sidebar">SIDEBAR</div>
                <div class="content">CONTENT</div>
            </div>    
        <div class="footer">FOOTEER</div>
    </div>

   

</body>
</html>

----------------------------------------------------------

body{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.menu {
    background-color:#B2D6FF;
    height: 100px;        
}

.sidebar {    
    float: left;
    background-color:#F09A9D;
    height: 300px;
    width: 30%;
}

.content {
    float:right;
    width: 70%;
    background-color:#F5CF8E;
    height:300px;
}

.footer {
    background-color: #D6E9FE;
    height: 200px;
}

.clearfix::before, .clearfix::after {
    content: "";
    display: table;
}

.clearfix::after {
    clear: both;
}

.clearfix {
    clear: both;
    *zoom:1;
}