<meta name="viewport" content="width=device-width, initial-scale=1">
		
#someElement{
  max-width:800px;
  width:calc(100% - 30px);
  height:200px;
  margin:0 auto;
}
		
#content{
  width:calc(100% - 180px);
  height:200px;
  float:left;
}
#navigation{
  width:180px;
  height:200px;
  float:right;
}
		
@media only screen and (max-width: 600px) {
    #content, #navigation{
        	width:100%;
        	float:none;
	}
}