dumping ground for all things html, CSS, java, web design, OOP -related. My "real" blog is TJPytheas.
A comprehensive guide by Sebastien Gabriel covering DPI/PPI, resolutions, retina, 4K, monitor hertz, all kinds of platforms and loads of practical tips:
This guide is designed as a “get started” or introductory read for the starting to intermediate designer who wants to learn or get more knowledge about cross-DPI and cross-platform design from the very beginning.
No complex math and un-parsable graph, just straight forward explanations ordered in short sections for you to understand and apply directly to your design process.