*{margin: auto; padding: 0; text-align: center;}
h1{text-align: center; padding: 0.5em;}
nav{float: left; width: 25%; background-color: #e3f2ff;}
nav img{width: 35%; margin: 5%; cursor: pointer;}
#principal{float: left; width: 75%;}
#visor{width: 60%; margin: 10%;}
#visor img{width: 100%;}