.clearfix:after {
  clear: both;
  display: table;
  content: '';
}

*{
  font-size: 10pt;
}

#body {
  margin: 0 auto;
  width: 960px;
}

#head {
  border: 1px lightgray solid;
  height: 50px;
  box-shadow: 2px 2px 2px #eee;
  margin-right: 5px;
  margin-left: 5px;
}

#intro, #banner, #contents, #foot {
  margin-top: 10px;
}

#intro>div {
  border: 1px lightgray solid;
  float: left;
  width: 228px;
  height: 250px;
  margin-right: 5px;
  margin-left: 5px;
  box-shadow: 2px 2px 2px #eee;
}

#banner>div {
  border: 1px lightgray solid;
  float: left;
  margin-right: 5px;
  margin-left: 5px;
  width: 468px;
  height: 100px;
  box-shadow: 2px 2px 2px #eee;
}

#contents-left {
  width: 708px;
  height: 300px;
}

#contents-right {
  width: 228px;
  height: 300px;
}

#contents>div {
  border: 1px lightgray solid;
  float: left;
  margin-right: 5px;
  margin-left: 5px;
  box-shadow: 2px 2px 2px #eee;
}

#foot {
  border: 1px lightgray solid;
  height: 30px;
  box-shadow: 2px 2px 2px #eee;
  margin-right: 5px;
  margin-left: 5px;
}

@media screen and (max-width: 980px) {
  #body {
    width: 760px;
  }

  #intro>div {
    width: 178px;
    height: 250px;
  }

  #banner>div {
    width: 368px;
    height: 100px;
  }

  #contents-left {
    width: 558px;
  }
  #contents-right {
    width: 178px;
  }
}

@media screen and (max-width: 780px) {
  #body {
    width: 560px;
  }

  #intro>div {
    width: 128px;
    height: 180px;
  }

  #banner>div {
    width: 268px;
    height: 100px;
  }

  #contents-left {
    width: 358px;
  }

  #contents-right {
    width: 177px;
  }
}

@media screen and (max-width: 580px) {
  #body{
    width: 320px;
  }

  #intro > div{
    width: 148px;
    height: 130px;
  }

  #intro > div:nth-child(1){
    display:none;
  }

  #intro > div:nth-child(4){
    display:none;
  }

  #banner > div{
    width:308px;
    height:100px;
  }

  #banner > div:last-child{
    margin-top:10px;
  }

  #contents-left{
    width:308px;
  }

  #contents-right{
    width:308px;
    margin-top:10px;
  }
}