Layout markup standard

HTML

<header></header>
<aside></aside>
<article></article>
<aside></aside>
<footer></footer>

CSS

header {
    width: 100%;
    height: 30px;
    background-color: red;
    margin: 0 auto;
    clear: both;
}
html {
    padding: 0;
    margin: 0;
}
body {
    max-width: 250px; /* This is a smell, it should be margin or padding in % on both sides, never do sizes of non-images in px */
    margin: 0 auto;
    background-color: yellow;
    overflow: hidden;
}
aside, article {
    float: left;
    height: 250px;
}
aside {
    width: 50px;
    background-color: magenta;
}
article {
    width: 150px;
    background-color: blue;
}
footer {
    width: 100%;
    height: 10px;
    margin: 0 auto;
    background-color: orange;
    clear: both;
}