.contenedor {background: #fff; width: 960px; margin: 0 auto 0 auto; }
.articulito {background: #ffe200; height: 250px; width:60% ; position: relative; float: left; box-sizing: border-box; margin: 20px 0px 20px 5%;}
.articulito2 {background: #ffe200; height: 250px; width:25% ; position: relative; float: left; box-sizing: border-box; margin: 20px 0px 20px 20px;}
header {background: #4add37; height: 200px;}
nav {background:#ff67e2; height: 50px;} 
main {background: #6339c3; height: 800px;}
section {background: #009dff; height: 499px;}
aside {background: #7c7b77; height: 299px;}
footer {background: #d0deb5; height: 100px;} 
section article {background: #ffe200; height: 400px; width:40% ; position: relative; float: left; box-sizing: border-box; margin: 5%;}