* {
    margin: 0px;
    padding: 0px;
}
#container {
    float: left;
    width: 100%;
    padding-right: 260px;
    margin-right: -240px;
    box-sizing: border-box;
}
aside {
    float: left;
    width: 240px;
    padding: 20px;
    background-color: #CCCCCC;
    box-sizing: border-box;
}
#columncenter {
    float: right;
    width: 100%;
    padding-left: 220px;
    margin-left: -200px;
    box-sizing: border-box;
}
#columncenter > div {
    padding: 20px;
    background-color: #999999;
}
#columnleft {
    float: left;
    width: 200px;
    padding: 20px;
    background-color: #CCCCCC;
    box-sizing: border-box;
}

.clearfloat {
    clear: both;
}