html {min-height: 100%; margin: 0; color: #008000; background: oldlace;}
   .header {
      float:top;
      width:100%;
      height:20%
    }
   .menu {
      float:left;
      width:19%;
      height:80%;
    }
    .mainContent {
      float:right;
      width:80%;
      height:80%;
    }