Mime types.. when will people learn?
HTTP has an incredible useful feature to supply the Content-Type HTTP header for any url. This allows HTTP clients to easily figure out what type of data they're getting.
Over and over again I see clients, not doing this and making assumptions based on the url. The extension of all things! This is some artifact inherited from ms-dos, and passed on to different operation systems when GUI's became popular.
Two clear examples I have today (and I'm sure many people will have examples like this)
- Flash's VideoPlayer component. If there's no extension in the url, it will assume its some kind of xml file.
- iTunes podcasts.. Files have to end with a known extension for iTunes to pick it up as a video or audio file. Even though the Mime type has to be specified in both the RSS feed and the HTTP Header!