styles.css

/* setup */

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

header,
section,
aside,
article,
footer { border: 1px dashed rgba(0, 0, 0, 0.2); }

header { background: rgba(255, 0, 0, 0.08); }
section { background: rgba(255, 255, 0, 0.08); }
aside { background: rgba(0, 255, 0, 0.08); }
article { background: rgba(0, 0, 255, 0.08); }
footer { background: rgba(255, 0, 255, 0.08); }

header:before,
section:before,
article:before,
aside:before,
footer:before {
  color: rgba(0,0,0,0.4);
  display: block;
  font: 16px/28px 'Helvetica Neue', Helvetica, Arial, sans-serif;
  height: 100%;
  padding: 10px;
  width: 100%;
}

header:before { content:"<header>"; }
section:before { content:"<section>"; }
article:before { content:"<article>"; }
aside:before { content:"<aside>"; }
footer:before { content:"<footer>"; }

/* layout 1 */
.layout-1 .container {
  margin: auto;
  width: 960px;
}

.layout-1 header { margin: 20px 0; }

.layout-1 aside {
  float: left;
  height: 400px;
  margin-left: 20px;
  margin-bottom: 20px;
  width: 300px;
}

.layout-1 article {
  float: left;
  height: 400px;
  margin-left: 20px;
  width: 600px;
}

.layout-1 section { overflow: hidden; }

.layout-1 footer {
  margin: 20px 0;
  clear: both;
}

/* layout 2 */

.layout-2 .container {
  margin: 20px auto;
  max-width: 1200px;
  width: 100%;
}

.layout-2 header {
  float: left;
  width: 25%;
  height: 550px;
}

.layout-2 section {
  float: left;
  overflow: auto;
  width: 50%;
}

.layout-2 aside,
.layout-2 article {
  float: left;
  width: 50%;
  height: 500px;
}

.layout-2 footer {
  float: left;
  width: 25%;
  height: 550px;
}

/* layout 3 */
.layout-3 .container {
  margin: 20px auto;
  max-width: 1200px;
  width: 100%;
}

.layout-3 header {
  float: right;
  width: 25%;
  height: 550px;
}

.layout-3 section {
  float: right;
  overflow: auto;
  width: 50%;
}

.layout-3 aside,
.layout-3 article {
  float: left;
  width: 100%;
  height: 250px;
}

.layout-3 footer {
  float:left;
  width: 25%;
  height: 550px;
}

/* layout 4 */

.layout-4 .container { }

.layout-4 header {
  height: 100px;
}

.layout-4 section {
  left: -150px;
  margin: 0 auto;
  position: relative;
  top: 50px;
  width: 800px;
  height: 600px;
}

.layout-4 aside {
  height: 400px;
  left: -50px;
  position: absolute;
  top: 100px;
  width: 200px;
}

.layout-4 article {
  height: 700px;
  position: absolute;
  top: 100px;
  left: 200px;
  width: 550px;
}

.layout-4 footer {
  height: 300px;
  position: fixed;
  right: 0;
  top: 150px;
  width: 300px;
}

/* layout5 */

.layout-5 .container {
  position: relative;
  max-width: 960px;
  margin: 50px auto;
}

.layout-5 header {
  height: 75px;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
}

.layout-5 section {
  float: left;
  position: relative;
  max-width: 730px;
  margin-top: 50px;
  width: 100%;
}

.layout-5 aside {
  height: 50px;
  left: -25px;
  position: absolute;
  top: 50px;
  width: 50px;
}

.layout-5 article {
  margin: 0 50px 50px;
  height: 600px;
}

.layout-5 footer {
  float: left;
  margin-top: 50px;
  margin-left: 30px;
  width: 200px;
  height: 600px;
}

/* layout 6 */

.layout-6 .container {
  text-align: center;
}

.layout-6 header,
.layout-6 section,
.layout-6 footer {
  display: inline-block;
  height: 300px;
  margin: 25px;
  text-align: left;
  width: 300px;
}

.layout-6 aside,
.layout-6 article { display:none; }

/* layout 7 - bonus */

.layout-7 section,
.layout-7 footer {
  display: none;
}

.layout-7 header {
  height: 400px;
  left: 50%;
  /* option 1: requires hardcoding
  margin-left: -300px;
  margin-top: -200px; */
  max-width: 600px;
  position: fixed;
  top: 50%;
  width: 100%;
  /* option 2: doesn't support legacy browsers (IE8) */
  -webkit-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}