> 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."
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."
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.
> 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."