a {
  position: relative;
  &:after {
    content: "";
    display: inline-block;
    position: absolute;
    bottom: -5px;
    left: 50%;
    // Don't work 'width: 0;' on IE10!!!
    width: 0%;
    height: 1px;
    background-color: currentColor;
    transform: translateX(-50%);
    transition: width .3s;
  }
  &:hover:after {
    width: 100%;
  }
}