In this technical presentation given at the San Francisco HTML5 User Group on April 6, 2012, PPK will explain why a pixel is not a pixel, what the differences between the desktop and mobile viewports are, and which bits web developers should care about.
PPK's Slides:
This event was organized by Marakana and Kaazing, and hosted at Adobe. If you're interested in learning more about HTML5 development, check out some of Marakana's HTML5 training courses.