There’s been a lot of debate among web professionals about whether or not it makes sense to server “retina” images to website visitors who’s devices support high pixel densities. In order to take full advantage of the sharpness of the new iPad’s screen, website owners would need to prepare their images at four times the number of pixels of normal (“72dpi”) web images.
I ran a few quick tests to see how much all those extra pixels affected overall file size. I used 130 randomly chosen jpeg images (all straight from my DSLR camera), and ran Photoshop and Irfanview batches to crop and scale them to a couple of often-used sizes. I used the same JPEG settings each time, and made sure the only difference between the images would be that the retina ones were four times sharper.
More Quick test: Retina images vs. regular ones