When accessing a file on a Microsoft IIS6 server, you may receive the following error:

The page cannot be found

[...]

HTTP Error 404 - File or directory not found.
Internet Information Services (IIS)

You may receive that error even for files that you know darn well do exist at the exact location you specified.

But Microsoft, no fan of simplicity, hijacks the specific and well-defined 404 status code to cover any number of possible problems with the request, which have nothing whatsoever to do with whether the page could be found.

If you check your logfiles in %WINDIR\System32\Logfiles (probably in a subfolder like W3SVC1), you may see some lines that end like this:

 ... 404 3 50

So that’s a "404.3" error, which apparently means that "[a file] extension is not mapped to a known extention [sic] in the MIME Map property."

Notice that the error displayed in the browser is not only entirely useless, it’s actually false.  Beyond that, it’s ridiculous that IIS fails to default to a sensible behavior like downloading the file anyway as a generic binary type, choosing instead to turn it into an error condition.

Just another way that Microsoft makes developers’ lives so much harder than they need to be...