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

#uno {
  
  height:70px; 
  margin-bottom:10px;
}
header,nav,section,article,footer,aside{
  border:1px solid black;
}

nav,section,aside{
  height:400px;  
  float:left;        
  margin-bottom:10px;
}

nav,aside{
  width:15%
}
section{
  width:65%; 
  margin-left:2%;
  margin-right:2.3%;
     
  
}
#cuatro {
  clear:both;   
  margin-top:10px;
}

#dos, article, #tres {
  height:20%;
  margin-bottom:15px;
  margin-left:auto;
  margin-right:auto; 
  width:90%;
}

#dos {
  margin-top:15px;
}

article {
  height:40%;
}