How come some site urls do not include a file extension?

Question

I was browsing the internet and noticed, YouTube, for example, contains a URL like this to denote a video page: http://www.youtube.com/watch?v=gwS1tGLB0vc.

Answer 1

Having or not having the extension is irrelevant. The browser acts on the MIME type returned by the server, not any extension used in the URL.