CSS

See: http://philipwalton.github.io/solved-by-flexbox/
See: https://github.com/AllThingsSmitty/css-protips/tree/master/translations/ru-RU
See: http://codeguide.co
See: http://cssnext.io/
See: https://drafts.csswg.org/
See: https://www.w3.org/Style/CSS/current-work
See: https://wsd.events/2016/11/26/pres/you-dont-know-css/
See: http://www.cheetyr.com/css-selectors
See: http://cssreference.io/
See: https://necolas.github.io/normalize.css/

Сетка

a[href]:not([class]) {
  color: #0000FF;
  text-decoration: underline;
}

.group:before, .group:after { content: " "; display: table; }
.group:after { clear: both; }
.group { zoom: 1; } /* IE 6/7 (trigger hasLayout) */

.hide-text {
  font: 0/0 a;
  color: transparent;
  text-shadow: none;
}