div#adv {
      background:#ccc;
      width:auto;
      margin:0;
      padding:0.5em;
}
div#nav {
      background:#ddd;
      float:left;
      width:25%;
      margin-right:0.5em;
      padding:0.5em;
}
div#main {
      background:#0fc;
      margin-left:25%;
      padding:0.5em;
}