layout-test-2col.css in Layout Plugin (obsolete, use core's Layout Discovery) 8

.layout-example-2col .region-left {
  float: left;
  width: 50%;
}
* html .layout-example-2col .region-left {
  width: 49.9%;
}

.layout-example-2col .region-right {
  float: left;
  width: 50%;
}
* html .layout-example-2col .region-right {
  width: 49.9%;
}