Good for accessibility, good for all users
In the early days of the Web, the web pages described the content and its structure, while the layout was decided by the browser. This allowed for content to be displayed on a lot of different devices, including text-only devices and devices without colour screens. This also opened up for the content display to adapt to the needs of the user.
At Opera, we grasped this opportunity with both hands. Clearly, if the user needed print that was 4x bigger and with a black background and green text, that is what we should show. However, not everyone agreed. I remember being at one of the early conferences and being threatened with legal action unless we displayed the content 100% the same way as it was shown by the leading competitor, which I believe was