.clearfix:after,
.cols:after
{
    content: ".";
    display: block;
    height: 0;
    clear: both;
    visibility: hidden;
}

.cols .col { float: left; }
.two_cols .col { width: 50%; }
.three_cols .col { width: 33%; }
.three_cols .col2 { width: 34%; }
.four_cols .col { width: 25%; }

.cornered { position: relative; z-index: 1; }
.tl, .tr, .bl, .br { position: absolute; z-index: 2; }
.tl, .tr { top: 0; }
.tr, .br { right: 0; }
.br, .bl { bottom: 0; }
.bl, .tl { left: 0; }