I have a small (Rails 3.1) app running on Heroku (with images also served from Heroku) The images load progressively (from top to bottom). If I take the same images and place them on another (Apache) server, they seemingly pop into existence once they are loaded.
So why are they loading top-to-bottom on Heroku? Is it just that they are loading really slowly (so the progressive download is obvious) or is it something to do with the way Heroku serves images?