I think Michael is right on. There is no comparison between a web image at 72ppi in sRGB and a big print at 360dpi in ProPhotoRGB. There are color shifts, noise, and other things that detract from a fine art print seen in person. However, for judging composition, the "artist's eye", and for gaining exposure for your work, I think the web is a valuable tool. The important thing is that we know and understand its limits. But without photography on the internet. I would've missed out on the work of many artists whose work I was first exposed to on my LCD screen at home.