hide image broken icon and replace it with alt content

image_broken_replacement.scss

img[alt] {
  position: relative;
  &:after {
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    /* Add bg color and the text of the alt attribute in place of the broken image */
    background-color: #999;
    font-family: 'Helvetica';
    font-weight: 300;
    line-height: 2;
    text-align: center;
    content: attr(alt);
  }
}