*{
	box-sizing:border-box ;
	padding: 0;
	margin: 0;
}

header{
	background-image: url(ZIB.JPG);
	background-repeat:no-repeat ;
	background-attachment: fixed;
	background-size: cover;,
	background-position:center;
	height: 4500px;
	width: 100%;
	position: absolute;
	padding:5rem 0 ;
}



header:before{
	position:absolute;
	content:"";
	background-color: blue;
	top: 0;
	left: 0;
	right: 0;
	bottom: 0;
	opacity:0.3 ;
}

.caja{

	background-color:white ;
	width: 150px;
	height: 150px;
}



.contenido-header{
	position: relative;
}

h1{
	color: white;
	text-align: center;
	font-size: 3rem;
}