The multipliers refer to the ratio of device pixels to software pixels ("CSS pixels"). Content can be negotiated via viewport size, it's just that Webkit doesn'

The multipliers refer to the ratio of device pixels to software pixels ("CSS pixels"). Content can be negotiated via viewport size, it's just that Webkit doesn't support that part yet. [0] The pixel ratio is better information than DPI, and connection speed is a difficult and unreliable metric. [0]: http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content-1.html#attr-img-srcset http://www.whatwg.org/specs/web-apps/current-work/multipage/...