PNG images are not displayed!

I met an especially obnoxious situation where I had deployed a perfectly working control library on a server and then, when testing how it worked using the remote browser on that server, I noticed only some of the resources where displayed. Mainly, some PNG files where not loaded.

Funny enough, if I went to the properties of the displayed images I saw their correct size. That actually meant that they were loaded correctly, so it wasn't a WebResource.axd issue. The remote browser was Internet Explorer 7, which has no problems displaying the PNG format. After changing all the images to GIF, I also found a solution for that problem.

Some "security" feature in Windows, especially Windows Server 2003 SP1, but also in SP2, messes with some PNG images being displayed. Probably, that security option was implemented to fix this issue. Here is the Microsoft knowledge base article detailing the fix.