Affiliate Marketing Secrets

I’m working on the beginnings of a few websites for some organizations I am affiliated with, and I had this thought: I know the traditional view is that screens project at 72/96ppi, but I know this is not the case as a computer screen goes by the actual pixels and not dpi/ppi (a 357px by 423px image will display that many pixels regardless of monitor resolution…it will just look “bigger” or “smaller” depending on the resolution). So my question is, as I’m designing my site(s), does it really matter what resolution I design at? 300 so I can see more detail? Any clarification will certainly help! Thanks in advance!