The key thing to keep in mind is resolution. An image online that covers the entire width of the Quora page would be less than 1000 pixels wide. If that photo is as tall as it is wide, it's a 1 megapixel photo (1,000 x 1,000 pixels) If you take that photo and print it in high quality (300 dots per inch), it would be quite small (8.4 x 8.4 cm / 3 x 3 inches). So, if you are looking to buy / commission / create photographs that work both in print and on screen, then worry about print resolutions, not about the resolution on screen.
The second thing you need to worry about, is sharpening the image for its target output medium. Glossy magazines need the photos sharpened differently than if you want to show it on screen, or print it on newsprint. Cambridge in Colour has a great Guide to Image Sharpening.