iPhone 5 screen size VS CSS media query [duplicate]

Answer 1

The iPhone's Retina display means the 1136x640 screen uses 568x320 virtual pixels. Each CSS pixel is made up of four physical pixels (2x2).

Since no one who says "give me a 100px wide div here" in CSS wants it to show up at half-size on a higher-resolution device like a Retina display, it doesn't use the physical pixels as CSS pixels.

Answer 2

The Retina display contains twice as many pixels as the standard display, but iOS treats the resolution as the standard display for measurement and screen output. If it didn't, websites would all look very tiny and zoomed out.