github.com/frontend-guidelines – Frontend Guidelines
shouldiprefix.com – What CSS to prefix?
w3layouts.com/css3-link-hover-effects – Demo Css3 Link Hover Effects
www.webdesignerdepot.com/3-cool-css3-image-hover-effects – 3 cool CSS3 image hover effects
www.devbattles.com/16+CSS3+Selectors+You+Should+Know – 16 CSS3 Selectors You Should Know
css-tricks.com/css-font-size – px – em – % – pt – keyword
css-tricks.com/why-ems – Why Ems?
www.impressivewebs.com/understanding-em-units-css – Understanding em Units in CSS