Absolute centering of elements with CSS.

Advantages:
Cross-browser (including IE8-10)
No special markup, minimal styles
Responsive with percentages and min-/max-
Use one class to center any content
Centered regardless of padding (without box-sizing!)
Blocks can easily be resized
Works great on images

Caveats:
Height must be declared
Recommend setting overflow: auto to prevent content spillover
Doesn't work on Windows Phone

Source: http://codepen.io/shshaw/full/gEiDt