html {
  font-size: 1em;
  line-height: 1.5em;
  font-family: Verdana, Helvetica, sans-serif;
}

body {
  margin: 0;
  background: #f3f3f3;
}

.encabezado {
  text-align: center;
  background: #006699;
  border-bottom: 0.1em solid silver;  
  padding: 0.5em;
  }


.footer-principal {
  text-align: center;
  background: #006699;
  border-bottom: 0.1em solid silver;  
  padding: 1em;
  }

.principal {
  max-width: 900px;
  margin: auto;
  padding: 1em;
}

.caja1, .caja2, .caja3, .caja4 {
  background: #fff;
  border: 0.1em solid gray;
  padding: 1em;
  margin: 1em;
  box-shadow: 0 0 0.1em 0.01em black;
} 

.caja1, .caja2, .caja3, .caja4 h2 {
  font-family: 'Verdana', sans-serif;
  color: darkblue;
  text-shadow: 0.03em 0.03em 0.01em #000;
  letter-spacing: 0.03em;
}

.caja2 iframe {
    /*height:100%;*/
    width:100%;
    max-width:600px;
    max-height:692px;
}


.caja3 img {
    height:100%;
    width:100%;
    max-width:400px;
    max-height:492px;
}
.articulo {
  margin-top: 2em;
}

.solucion h2 { font-size: 1.5em; }

.solucion img {
    height:100%;
    width:100%;
    max-width:650px;
    max-height:400px;
	align-content:center; 
	overflow:hidden;
}