Once again, here is an example shown at the 100% view in Photoshop. This version of the picture has fewer pixels, and more of the picture can be seen at the 100% view.
On our "cartoon" screen, the picture looks terrible, but with real life monitors it looks much more reasonable.
Still, pictures that fit onto one computer screen at the 100% view are generally too small for quality printing at a reasonable print size. They simply don't have enough pixels. That is why pictures taken from the web are insufficient for quality printing.