Lesson Code: http://www.developphp.com/video/CSS/Viewport-Percentage-Units-CSS-HTML-Layout-Tutorial
Learn to use the new viewport length values in CSS to size elements relative to the viewing area. The way it differs from normal percentage lengths is that these lengths are always relative to the viewport and not relative to their parent elements. It also helps to make text and other elements sized relative to the viewing area.
Source: Adam Khoury