thecoalman - 1:48 am on Jan 11, 2013 (gmt 0)

I've read that 'the average person' has difficulty seeing the difference of images above 300 dpi.

Again, it's irrelevant for browsers or even displays for the most part. 300dpi isn't even achievable on any standard monitor , the "retina displays" from apple come close but they have fairly small physical dimensions operating with high resolutions.

Let me restate this, let's say we have 2 images that are 200px*200px. One is set at 72dpi and the other is set 1000dpi. When you display these side by side in a browser window they are going to look identical, they are going to take up the exact same amount of real estate and even have the nearly the same file sizes. The only reason it's not the exact same file size is those extra 0's in the meta data add a byte or two.