Retina tests

Load this page on a retina device such as iPhone 4, iPhone 4S or the new iPad.

What am I testing here?

Figure 1 shows a normal image in a web page. On a retina display, the edges would look blurry.
Figure 2 is two times bigger but rendered in 300×300px dimension, so it will look good on a retina display.
Figure 3 is upsized from Figure 1, with nearest-neighbour resampling. This is to emulate non-retina rendering on a retina display.
Figure 4 is the same as Figure 2 but aliased. I'm just wondering if anti-aliasing is still needed on a high pixel density display. Turns out the answer is yes.
Figure 5 is two times bigger, aliased. Slightly better but not great.