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The article says, > The way the CSS authors handled this problem (again, sensibly, IMO), was to allow the user agent (ie. the browser) to choose a useful preci

The article says, > The way the CSS authors handled this problem (again, sensibly, IMO), was to allow the user agent (ie. the browser) to choose a useful precise size for the “px” unit and then size all the other units relative to that “px” unit. So I'm a little confused about what you mean when you say, "Nope! "px" is defined by the CSS spec."

svachalek 13y ago
According to the article, it's defined as an integer number of pixels approximating 0.265mm (SI). So the size will vary but this is a long way from "whatever the device+OS combo wants it to be."
jahewson 13y ago
These are both correct. The CSS 2.1 spec actually defines a CSS pixel ("px") as "the whole number of device pixels that best approximates the reference pixel". It's to allow a little leeway for devices with low-resolution screens. On a high-resolution screen a CSS pixel should be = the reference pixel.
- Macha 13y ago
  To the best of my knowledge, on iOS, 1 CSS px has been 2 device pixels for a while. Might even be 4 device pixels on Retina devices.
  - jahewson 13y ago
    Right, so a CSS pixel is equal to the reference pixel in size.