a11y.scss

@mixin visuallyHidden {
  // remove external box decoration
  border: 0;
  outline: none;
  box-shadow: none;
  // shrink as small as possible without removing 
  // content from the accessibility tree
  width: 1px;
  height: 1px;
  // eliminate any space being taken up by the element
  margin: -1px;
  overflow: hidden;
  padding: 0;
  // remove element from normal document flow
  position: absolute;
  z-index: -10000;
  // render fg and bg invisible
  color: transparent;
  background-color: transparent;
  text-shadow: none;
}