Maybe somebody can enlighten me: I've noticed that many people who sell pictures on the Net give size information in DPI, like the pictures are "300 DPI" or "72 DPI". But this is meaningless without any dimensions in inches. If I open a picture and change its info from 200 DPI to 300 DPI without rescaling, I have not changed anything meaningful about the picture at all, except how big my printer decides to print it.
So, are all those people confused, or am I missing something?
[A different issue is that when people use "DPI" (dots per inch) they usually mean "PPI" (pixels per inch), but I've given up on that one.]