layout - 8 (flex)

    <style>
        * {
            margin: 0;
        }

        body {
            background-color: #E1F5FE;
        }

        #wrap {
            width: 1200px;
            margin: 0 auto;
        }

        #header {
            height: 100px;
            background-color: #BBDEFB;
            grid-area: header;
        }
        #nav {
            height: 100px;
            background-color: #90CAF9;
        }
        #main {
            display: flex;
        }
        #contents {
            width: 900px;
            display: flex;
            flex-wrap: wrap;
        }

        #aside {
            width: 30%;
            height: 780px;
            background-color: #64B5F6;
        }

        #article1 {
            width: 100%;
            height: 260px;
            background-color: #42A5F5;
        }

        #article2 {
            width: 100%;
            height: 260px;
            background-color: #2196F3;
        }

        #article3 {
            width: 100%;
            height: 260px;
            background-color: #1E88E5;
        }

        #footer {
            height: 100px;
            background-color: #0A78DD;
        }

        @media (max-width: 1300px) {
            #wrap {
                width: 96%;
            }

            #article2 {
                width: 50%;
                height: 520px;
            }

            #article3 {
                width: 50%;
                height: 520px;
            }

        }

        @media (max-width: 768px) {
            #wrap {
                width: 100%;
            }
            #contents {
                width: 900px;
                flex-direction: column;
            }
            #article1 {
                width: 100%;
                height: 390px;
            }
            #article2 {
                width: 100%;
                height: 390px;
            }
            #article3 {
                display: none;
            }
        }

        @media (max-width: 480px) {
            #contents {
                width: 900px;
                flex-direction: column;
            }
            #aside{
                display: none;
            }
            #article1 {
                width: 100%;
                height: 200px;
            }
            #article2 {
                width: 100%;
                height: 430px;
            }
            #article3 {
                width: 100%;
                height: 150px; 
                display: block;
            }
        }
    </style>​

    <div id="wrap">
        <header id="header"></header>
        <nav id="nav"></nav>
        <main id="main">
            <aside id="aside"></aside>
            <div id="contents">
                <article id="article1"></article>
                <article id="article2"></article>
                <article id="article3"></article>
            </div>
        </main>
        <footer id="footer"></footer>
    </div>