When I worked pre-press at the print house, this is how we explained it to customers that wanted to supply their own artwork: 300 dpi at the size you want the job printed is good for color. 600 dpi at the size you want the job printed is good for fine lines, like small point-sized text, for example. Monitors display slightly higher than 72 dpi, so a 300-dpi image should look *slightly better than a 72-dpi image on-screen -- but only marginally so. What is more important is the dimensions of the image. This confuses a lot of people, because they know they can change the resolution of their monitors from 800x600 to 1024x768, etc. -- but these are pixel dimensions, not the dpi resolution -- which is always going to be the slightly-more-than-72 dpi mentioned previously. Hope this helps :-)