If you are missing something, it is because I explained it badly, or you're using a browser that operates differently from FireFox, or both
Tell me more ... (about your screen, browser, etc.)
If you use browser zoom (i.e. by not doing Ctrl 0), it WILL look soft and in these images it
really isn't necessary, given their large size. Using browser zoom on an image, especially one that is big enough, is akin to paying for an expensive lens, then always shooting through the car window glass and wondering it isn't sharp. OK slightly dodgy analogy, but it is that fundamental.