CodePen.io is an online code editor that allows you to develop in an open-source environment. You create 'pens' which display a live-preview as you code which is great for testing out bugs, collaborating and discovering the latest design patterns.

21 Modern CSS menu examples. 19 Stylish CSS forms. 23 Fantastic CSS Hover Effects. 19 CSS Border Animations you can implement. 15 Stylised CSS Tables. 13 Pure CSS Dropdown Menus. 15 Creative CSS Filter Examples. 35 Unique CSS Text Effects. 15 CSS Sliders you can use.