I wonder if you think about canvas size when you are prepairing things for the web. Just as graphics for print has to fit certain defined sizes, ie, busines cards, and brochures. Designing for the web you need to think about screen "real estate". I think it's nice to have to scroll to see the whole thing but because screen size is so important to the composition you might set your monitor at 640 x 480 just to see what the majority of monitors see when they load the art.