available to screenreaders.
        See notes in cookbook recipe. 
        https://github.com/h5bp/html5-boilerplate/issues/1985#issuecomment-394096182
        https://medium.com/@matuzo/writing-css-with-accessibility-in-mind-8514a0007939 
        */
      .visuallyhidden {
        border: 0;
        clip: rect(0 0 0 0);
        height: auto;
        margin: 0;
        overflow: hidden;
        padding: 0;
        position: absolute;
        width: 1px;
        white-space: nowrap;
      }

