Untitled

nav {

    height: 50px;
    margin: auto;

}


#lewy {
    width: 200px;
    height: 900px;
    margin: auto;

    float: left;

}
#jd {
    width: 1200px;
    height: 900px;
    margin: auto;

    float: left;
}
#prawy {
    width: 200px;
    height: 900px;
    margin: auto;

    float: left;

}
footer {
    width: 1600px;
    height: 50px;
    margin: auto;

    float: right;
    clear: both;
}
main{
    width: 1600px;
    height: 1000px;
    margin: auto;

}
<!DOCTYPE html>

<html lang="pl">
<head>
    <meta charset="utf-8" />
    <link rel="stylesheet" href="1.css" />
    <title>kozak szablon oguem</title>
</head>
<body>
    <main>
    <header></header>
    <nav></nav>
    <aside id="lewy"></aside>
    <div id="jd"></div>
    <aside id="prawy"></aside>
    <footer></footer>
    </main>
</body>
</html>