body {
	background-image: linear-gradient(to bottom, white, black); /* fundo cinza */
	font-family:Arial;
	
	
A:link {text-decoration:none;color:#0000cc;} 
A:visited {text-decoration:none;color:#ffcc33;} 
A:active {text-decoration:none;color:#ff0000;} 
A:hover {text-decoration:underline;color:#999999;} 

	}
	
#pagina {
	width:1000px;
	margin:auto;
}
	
header,footer { /* evitar código repetido */
	background-color:#666666;
	color:#FFFFFF;
	text-align:center;
	font-size:30px;
	padding:40px 0;
	}
#colunas {
	display:flex;
}	
nav,aside {
	background-color:#333333;
	color:#FFFFFF;
	height:500px;
	flex:1;
}
article {
	background-color:#CCCCCC;
	height:200px;
	flex:3;
}