Reference: "Object-as-Image: (...) If no type is given, then Internet Explorer must try to determine what the object is based on any additional attributes provided (classid, codetype, etc.) or solely by the URL if no additional attributes are provided (by getting MIME type information from the server)." (quote from HTML Improvements and Acid2: Internet Explorer 8 Beta 1 for Developers, page 4, available from Internet Explorer 8 Beta 1 Whitepapers) released on March 5th 2008.
Firefox 3, Opera 9.64, Safari 4.0 beta, Konqueror 4.2.0, Seamonkey 1.x, Seamonkey 2.x, NS 7.2, K-meleon 1.x all pass this test.
This bug has been reported at connect's IE beta feedback as bug 389191.
I see a red "X", as if the image doesn't exist at the specified location (or failed to render), but the frame takes its space, and the alternate text doesn't appear. If I right click and select "Properties", then open up the address in a new tab or window, I do get the image however.
I'm running IE8 RTW with the default settings for everything (Security, Privacy, Advanced), and by "Default", I mean the settings you get when you click on the buttons ("Reset all zones to default level", "Default" and "Restore advanced settings" respectively). The same behavior is observed in no add-ons mode too.
I have Windows Vista Ultimate x64 SP1 with all updates from Windows Update installed (...) I have the PNGs associated with "Windows Photo Gallery". I have other graphical software that can work with PNGs (Adobe Photoshop CS4), but neither it or another program has ever tweaked this settings before (or at least I don't know if it did). I've had my IE8 RTW installation upgraded from RC1 in case it matters.
An IE 8 beta tester
As soon as an application takes the "association" of png, things changes. IE tries to use this application to display the object, and this may work or not (QuickTime works, another one that I have don't and the alternate text is displayed).
Removing the association with the application seems to create further problems, including more cases when the alternate content is displayed. This probably depends on how the de-association is done (many applications have options to do this, which do not seem to work consistently).
The only sure way to restore the correct behavior seems to be the complete removal and recreation of the file type 'PNG Image' (in this way it is automatically associated to "windows picture and fax viewer").
All this behavior is surely not correct. Jpegs are also usually associated to different applications, but do not have this problem. (of course the fact that the problem only occurs when no mime type is specified makes it less important).
An IE 8 beta tester
I've played around. Windows offered me to choose Opera (9.64) to open .png files by default. With Opera set as .png handler, IE8 displayed only the alternate text. The same happened when I set MS paint as the .png handler. (...)
It seems IE's image code is related to the software the images are associated with. It shouldn't.
An IE power user
Fails for me on an Xppro 64bit viewed in Internet Explorer 8 with no addons
(Your message browser Failed...alternate content appeared)
Png images are opened with Faststone Image Viewer
Rose Weir in comp.infosystems.www.authoring.html newsgroup