It\'s got nothing to do with browsers scaling or anything like that. Each display device has a different pixel resolution. Surely you understand this?
You could have two monitors, one 15\", the other 21\", but both displaying a 1280 x 960 screen. Both monitors will exhibit an identical amount of detail, but obviously the picture will appear much smaller on the 15\" monitor as it is using smaller pixels.
Yes, each display does have a different pixel resolution. However I thought that most modern, common, displays were approximately 95dpi, give or take a bit, at least as far as desktop monitors were concerned. So while it will not be perfectly accurate across the breadth, it will be reasonably accurate for most everyone. Elaboration:
A 15 inch monitor with a native resolution of 1024x768, which is completely common, very likely has around 97dpi. A 21 inch with a native resolution of 1600x1200 has about 101dpi. That isn\'t a lot of variance.
Now of course the Zaurus c series at 640x480 at has a much higher dpi than these, but I really wasn\'t trying to consider mobile devices, as most people with the Zaurus don\'t need an image to convey to them the size of the keyboard.
In the case of a 15 and 21 inch both doing 1280x960. The 15 inch would STILL have a native dpi of approximately 97 because the monitor is built at a certain specification based on the size and technology of the time. It can, however, be over driven. Likewise with the 21 inch, although it would be underdriven at that point.
I realise you probably know all of this already, but I felt compelled to justify myself a little.
