How you decide to style the header row depends a lot upon what is in it. If your header row is just going to have a logo graphic and headline, then using a headline tag <h1> makes more sense than using a <div>. You can style your headline the same way you would style a div, and you avoid extraneous tags and "divitis".
The HTML for my header row goes right at the top of the container and looks like this:
<h1>My Header Row</h1>Then, to set the styles on it, I added a red border on the bottom, so you could see where it ends, zeroed out the margins and padding, set the width to 100% and the height to 150px:
#container h1 {
margin: 0;
padding: 0;
width: 100%;
height: 150px;
float: left;
border-bottom: #c00 solid 3px;
}Don't forget to float this element with the float: left; property. The key to writing CSS layouts is to float everything - even things that are the same width as the container. That way, you always know where the elements will lay on the page.
I used a CSS descendant selector to apply my styles only to H1 elements that are inside the #container element.
