#bloques_izq {
	float:left;
  	width:225px;
	margin-top:5px;
  	margin-left:20px;
  	margin-right:10px;
  	margin-bottom:5px;	
}

#cuerpo {
	padding-top:5px;
	margin-top:0;
  	margin-left:260px;
  	margin-right:260px;
  	margin-bottom:5px;
  	text-align:center;
}

#bloques_der {
	float:right;
  	width:225px;
	margin-top:5px;
  	margin-left:10px;
  	margin-right:20px;
  	margin-bottom:5px;
}