html:
<body>
<div id="header">
This is HEAD!
</div>
</body>
or
<!-- html5 -->
<body>
<header>
This is HEAD!
</header>
</body>
css:
<head>
<style type="text/css">
#header { /* #header <- (specify as id) -> id="header" */
height: 40px; /* specify height and width */
width: 300px;
background: url(images/yourimage.jpg); /* your background image */
}
or
header { /* html5 */
height: 40px;
width: 300px;
background: url(images/yourimage.jpg);
}
</style>
</head>