*
{
	margin:0px;
	padding:0px;
}
#principal
{
	width:100%;
	height:520px;
	margin:auto;
}
header
{
	margin:10px;
}
h1
{
	font-family:helvetica;
	font-size:20px;
	text-align:center;
}
article
{
	float: left;
	width: 44%;
	height: 460px;
	font-family: Tahoma;
	font-size: 16px;
	margin: 5px;
	padding-top: 20px;
	text-align: center;
	
}
aside
{
	width:53%;
	height:430px;
	float:right;
	margin:5px;
	font-family:Tahoma;
	font-size:12px;
}