I once worked with a fellow that called and asked if we could make the images on his site exactly 7 inches wide. I asked him to measure his screen side to side, adjusted the image and asked him if that’s better. He said yes, much better. Then I asked him if anyone in the office has a different size monitor, and could he measure the image on their screen. He came back and sheepishly said it’s a different size. I explained that because of different monitors and devices, ratio works better than inches. He said thanks and was much more receptive after that. If people knew what designers and developers know, they wouldn’t need us.