Open fonts at Libre Graphics Meeting 2009

Firefox does not use "pixels" that way, and neither does CSS. CSS pixels actually correspond to your angle-of-view suggestion, and the spec defines a precise optical angle for them. Thus far most screens lack sufficiently high resolution to really demonstrate this, but it's my understanding that if you grab a high-res screen and run Firefox (3.5 at least, I believe 3.0 as well) on it, a pixel as selected by CSS does not exactly correspond to what the spec names as a "device pixel".

Frankly, having used for brief times a 30" screen, the bigger problem is that there's so much space that no website or application can fill it, and window maximization is an obsolete concept because seek times across its height and width at a normal distance for a computer screen are so atrocious. That's arguably a window manager problem, but I can imagine individual applications might take various steps to better use that space.