I have encountered an annoying bug with internet explorer on a javascript animation I made.
I have a greyscale image of a city skyline which fades its opacity to 0, revealing a full-color skyline.
It looks great in all other browsers, but IE reveals artifacts. A friend told me this is because of some weird bug with animating opacity with javascript in IE. Something to do with anti-aliasing and an assumed black background? I don’t really know.
Easiest fix – change the images to gifs. Since you’re city image doesn’t have any gradients, the advantage of the alpha channel support in the png format is not really anything you need. This should work all the way back to ie6.