*{box-sizing:border-box;}.menu{float:left;width:20%;}.menuitem{padding:8px;margin-top:7px;border-bottom:1px solid #f1f1f1;}.main{float:left;width:60%;padding:0 20px;overflow:hidden;}.right{background-color:lightblue;float:left;width:20%;padding:10px 15px;margin-top:7px;}@media only screen and (max-width:800px){.main{width:80%;padding:0;}.right{width:100%;}}@media only screen and (max-width:500px){.menu, .main, .right{width:100%;}}