Tricks to Identify the Technologies that a Web Site is Using

I have been asked several times to identify the technologies that a particular web site is using  (from Operating System , Webserver , Javascript Framework and so on… Sometime it it very straighforward other times it is just like searching a needle in a haystack. Note that you cannot just look at the file extension to say that a website is using asp or php, you will need to dig deeper.

Here are the trick that I usually use (from the most intuitive to the least intuitive):

ONLINE TOOLS

General Info, Web server, CMS, OS…

http://builtwith.com/
http://news.netcraft.com/
http://www.quarkbase.com/
http://w3techs.com/sites

Domain Details

http://dndetails.com/
http://whois.domaintools.com/

Javascript Framework

http://nouincolor.com/wtframework/2.0/

SEO Info

http://www.alexa.com/

MANUALLY

1. If you look at the source code , if you are familiar with WordPress, Drupal and other CMS  you can easily find them by looking at the source code.
2. The CSS files can reveal a lot of information about the framework being used.