"We still frequently hear the very bad advice: 'Computer video screens show images at 72 dpi, so scan all your images for the screen at 72 dpi'. This is incredibly wrong; it simply doesn't work that way.
Regardless what you may have heard almost everywhere, there is no purpose or reason for 72 dpi images on computer video screens or web pages. As a concept, 72 dpi is simply a false notion. It is a myth. It is NOT how video works, and it is detrimental to understanding how things really do work. It is very easy to show proof of this here."