hidden an element in sass From http://zerosixthree.se/8-sass-mixins-you-must-have-in-your-toolbox/

hidden.scss

%visuallyhidden {
  margin: -1px;
  padding: 0;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip: rect(0, 0, 0, 0);
  position: absolute;
}