The link PNGs appear darker, except for Email A Friend, which has the gAMA chunk removed.
In setting up the new vehicle details page for DDC, I noticed that the background color for the 24-bit PNGs did not match the css background color, but only in IE6.
Searching online, I found this is a known bug with IE that stems from a flawed interpretation of the PNG’s gAMA setting. It’s fantastic that the IE team added PNG alpha transparency to IE7, but apparently they kept the gAMA bug in IE7 to make sure browser compatibility specialists keep their jobs for years to come.
In short, the fix is to remove the gAMA chunk using a tool such as TweakPNG or Pngcrush — I used TweakPNG (freeware, super easy to use, no installer) which worked great for fixing one image at a time. Fun stuff.