body,html {
width: 100%;
}
* {
margin: 0px;
padding: 0px;
}
@font-face {
    font-family: "Fira Sans";
    src: url(FiraSans-BookItalic.ttf) format("truetype");
}
#cabeceras{
width: 100%;
height: 40px;
text-align: center;
margin-top: 10px;
}
#contenido {
margin: 0px auto;
border: 1px solid black;
background-color: #AEE;
font-family: Fira Sans, helvetica;
}
#marco {
    display: -webkit-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;

    -webkit-flex-wrap: wrap;
    flex-wrap:wrap;
	}
header {
width: 100%;
height: 100px;
text-align: center;
background-color: #AAF;
}
header h1 {
padding: 20px;
}
#contenidos {
height: 500px;
width: 100%;
}
iframe {
top:10px;
width:25%;
height:450px;
}
video {
width: 45%;
margin-top: 10px;
margin-left: 25px;
}
#imagenes {
width: 25%;
float: right;
}
footer {
width: 100%;
height: 60px;
text-align: center;
border: 1px solid blue;
padding-top: 30px;
background-color: black;
color: white;
}
h2 {
text-align: center;
}
#izquierda {
float: left;
width: 25%;
}
#centro {
float: left;
width: 45%;
}
#derecha {
float: right;
width: 30%;
}