A friend of mine who's a graphic artist and does a lot of print work asked about CMYK vs RGB.
It started when a webpage photo wouldn't show in a client's browser, but she saw it in her's. The first place to look was reference - was the graphic being referenced from her local disk so she saw it but the rest of the world would not? No, the reference was correct and the file was on the server where it should be, so she asked me what was wrong. She wanted to know if it was a DotNetNuke issue, since the site was built using DNN.