I've mentioned this before and I'm not the first to say it, but it's time to stop using px and start using in its place absolute measurements like inches or millimeters. It's the only sane approach to supporting different resolution displays.
Absolute measurements (which no longer exist in CSS) are a sane approach to support different resolution displays that are all used at the same viewing distance.
Using absolute measurements to size things on a web page that is then viewed on a TV (viewing distance in the 5-15ft range), a tablet (viewing distance in the 1-2ft range), and an eyeglass HUD (viewing distance in the 1-3in range) would be a disaster.
The fact that people _were_ using inches and millimeters on the web and expecting them to somehow work across all these devices is why they're all now defined in terms of CSS reference pixels...
Unfortunately, devices stopped actually making "mm" a millimeter long a while ago; for instance, various mobile devices scale "mm" by a factor of 2 because they assume that sites don't actually want a physical unit of measure.
