Is there a way to identify which web framework is used in a site?

Whenever I come across a cute website, I am always curious to know which web framework was used by its developers?

Being a novice in web development, a look at the page source doesn't give any clue.

Any way(s) to get this i开发者_如何学运维nformation? If possible, may be with a bit of Ruby magic, I can figure out things like: which is the most/least used framework for my favorite sites, audio/video heavy sites, etc.

Sometimes you can based on the URL patterns, or which scripts are included in the site ... but it's not a 100% predictor. You can write a site that completely masks the framework and simply delivers HTML/JS to the browser