You might have a logo which is 50 by 50 pixels, but you could label it in HTML as being 100 by 100. It will then appear large, even though it was a small file which loaded quickly. This works best in graphics which feature no sharp edges, like white clouds in a blue sky, or in graphics with sharp horizontal and vertical edges, no diagonals and no anti-aliasing. Colored text might not print as neatly on either a color or monochrome printer. The worst situation occurs when you use white text on a dark background.
Screen space is much cheaper than paper.
Pouring in a heap of undisciplined text causes your screen to fill with text, border to border. That's like a newspaper page with only one column and no margins. For low-vision monitor users, narrower columns can be easier to read. This will be true no matter how big the monitor, no matter what the screen resolution is, and no matter the type size used. In this page, I have put the text into a table which is 325 pixels wide.