Relative + fixed

HTML

<header>
        <h1>Title should scroll</h1>
        <nav>Nav should be fixed</nav>
    </header>
    <article style="height:1500px;">
        <p>Article should scroll</p>
    </article>

CSS

body { margin: 20px; }

/*  positioning scheme, using negative margins, 
    due to a tricky layout, both fixed, centered and fluid  */

header, article {
    position: relative; 
    width: 600px;
    left: 50%;
    margin-left: -300px;
    }

nav { 
    position: fixed;
    }
article p { 
    margin-left: 200px;
    }