@import url('https://fonts.googleapis.com/css?family=Roboto:400,500,700,900');

*{font-family: "Roboto";
}

<meta name="viewport" content="width=device-width, initial-scale=1.0">

header{
color: black;
}

.cajaarriba {
display:flex; 
flex-direction: column;
align-content: center;
justify-content: center;
text-align: center;
}

div img{
margin-bottom: 0.4rem;
}

div h1{
font-size: 1.7rem;
letter-spacing: 0.1rem;
font-weight: 700;
margin-top: 0rem;
margin-bottom: 0.3rem;
border-top: 2px;
}

div p {
font-size: 0.5rem;
font-weight: 400;
letter-spacing: 0.1rem;
text-transform: uppercase;
margin-top: 0;
margin-bottom: 0.5rem
}

nav ul {
margin: 0.7rem;
padding-left: 1rem;
padding-right: 1rem;
box-sizing: content-box;
display: flex;   
text-transform: uppercase;
text-align: center;
list-style: none;
justify-content: center;
align-items: center;
font-size: 1.3rem;
background-color: black;
flex-wrap: wrap;
}

nav li{
font-weight: 500;
padding: 0.5rem;
line-height: 1.1rem;
letter-spacing: 0.05rem;
}

nav a{
font-size: 0.55em;
text-decoration: none;
color: white;
}

main{
display: flex;
flex-direction: row;
justify-content: center;
flex-wrap: wrap;
}

article1{
margin: 2em;
display: flex;
flex-direction: column;
justify-content: space-between;
align-items: flex-start;
}

article2{
margin: 2em;
display: flex;
flex-direction: column;
justify-content: space-between;
align-items: flex-start;
}

article3{
margin: 2em;
display: flex;
flex-direction: column;
justify-content: space-between;
align-items: flex-start;
}

h2{
font-size: 1.2em;
letter-spacing: 0.1em;
margin-top: 1em;
margin-bottom: 0.5rem;
border-bottom: 2px solid black;
}

main p {
margin: 0;
font-size: 0.8em;
}

aside {
margin: 0;
display: flex;
flex-direction: column;
text-align: center;
}

h3{
margin-top: 0.5rem;
text-decoration: underline;
margin-bottom: 0.5rem;
font-size: 0.7rem;
font-weight: 600;
letter-spacing: 0.1rem;
text-transform: uppercase;
}

div{
display: flex;
flex-direction: column;
justify-content: space-around;
font-size: 0.5rem;
font-weight: 400;
letter-spacing: 0.1rem;
}

h4{
margin: 0.5rem;
}

footer{
margin: 1rem;
display: flex;
flex-direction: column;
justify-content: center;
}

footer{
margin: 1rem;
border-top: 1px solid black
}

footer p{
text-align: center;
font-size: 0.6rem;
color: black;
}