_clearfix.less

/**
 * For modern browsers
 * 1. The space content is one way to avoid an Opera bug when the
 *    contenteditable attribute is included anywhere else in the document.
 *    Otherwise it causes space to appear at the top and bottom of elements
 *    that are clearfixed.
 * 2. The use of `table` rather than `block` is only necessary if using
 *    `:before` to contain the top-margins of child elements.
 */
.cf {
  &:before, &:after {
    content: " "; /* 1 */
    display: table; /* 2 */
  }
  &:after{
    clear: both;
  }
}
//from: http://nicolasgallagher.com/micro-clearfix-hack/