You can usually get a better guess by looking at the content of the page. Various technologies do tend to leave their marks. Although if a URL ends with a ".jsp", the app is probably Java, ".jsf" probably JavaServer Faces, ".do" likely Struts. And ".php" probably a PHP app. Although for a really complex app, a single URL context might get routed to multiple servers running multiple technologies.
When it comes to destroying a civilization, gas chambers cannot hold a candle to echo chambers.