<div id="wrap">
    <div id="header">
        <div class="container">
            <div class="header"></div>
        </div>
    </div>
    <div id="nav">
        <div class="container">
            <div class="nav"></div>
        </div>
    </div>
    <div id="main">
        <div class="contents container clearfix">
            <div class="cont1"></div>
            <div class="cont2"></div>
            <div class="cont3"></div>
            <div class="cont4"></div>
        </div>
    </div>
    <div id="footer">
        <div class="container">
            <div class="footer"></div>
        </div>
    </div>
</div>

*{
    box-sizing: 0;
    padding: 0;
    margin: 0;
}
#header {
    height: 100px;
    background-color: #EEEBE9;
}
#nav {
    height: 100px;
    background-color: #B9AAA5;
}
#footer {
    height: 100px;
    background-color: #4E342E;
}
.container {
    width: 1200px;
    height: inherit; 
    margin: 0 auto; 
}
.header {
    width: 100%;
    height: 100px;
    background-color: #D5CCC9;
}
.nav {
    width: 100%;
    height: 100px;
    background-color: #9D8980;
}
.main {
    width: 100%;
    height: 780px;
    background-color: #594139;
}
.footer {
    width: 100%;
    height: 100px;
    background-color: #3E2723;
}

.contents .cont1 {
    width: 100%;
    height: 100px;
    background-color: #684D43;
}

.contents .cont2 {
    width: 100%;
    height: 200px;
    background-color: #74574A;
}

.contents .cont3 {
    width: 50%;
    height: 480px;
    background-color: #594139;
    float: left;
}

.contents .cont4 {
    width: 50%;
    height: 480px;
    background-color: #4A352F;
    float: left;
}

 @media (max-width: 1220px) {
    .container {
        width: 96%;
    }
    .contents .cont1 {
        float: left;
        width: 30%;
        height: 780px;
    }
    .contents .cont2 {
        float: left;
        width: 70%;
        height: 390px;
    }
    .contents .cont3 {
        width: 35%;
        height: 390px;
    }
    .contents .cont4 {
        width: 35%;
        height: 390px;
    }
 }
 @media (max-width: 768px) {
    .container {
        width: 100%;
    }
    .contents .cont2,
    .contents .cont3,
    .contents .cont4 {
        width: 70%;
        height: 260px;
    }
 }

 @media (max-width: 480px) {
    .contents .cont1 {
        width: 100%;
        height: 150px;
    }

    .contents .cont2,
    .contents .cont3,
    .contents .cont4 {
        width: 100%;
        height: 210px;
    }
 }

 /* 
    float으로 인해 영역깨짐 방지법
    1. 깨지는 영역에 clear:both를 설정한다.
    2. 부모 박스 영역에 overflow: hidden을 설정한다
    3. clearfix를 설정한다
  */

 .clearfix::before,
 .clearfix::after {
    content: '';
    display: block;
    line-height: 0;
 }
 .clearfix::after {
    clear: both;
 }