Figure out what that site and server are running

If you administer or program websites etc., you often find yourself wondering what the specifics of a particular website or its server are. For e.g., you might want to know if a server is running on Linux, or if a site is based on Drupal or Mambo. The following sites all assist in this endeavour:

• Netcraft: One of the oldest sites to offer this service, Netcraft provides information about the webserver behind a site and its software as well as uptime, IP and WHOIS details. It is also useful to get a historical snapshot on the servers and software being used, IPs as well as the webhosting provider.
• BuiltWith: BuiltWith offers details on the webserver's OS and other capabilities as well as details about the site itself. These details can included the language of the site (such as PHP), JavaScript libraries in use (such as jQuery), widgets in use (such as Facebook like), advertising and tracking scripts and so on. It also provides recommendations on improving the site.
• Webmaster Coffee: Webmaster Coffee supplies information on the webserver in terms of its OS and installed software, the website including the language it is written in and JavaScript frameworks it is using, CMS details if available, and additionally, details from an SEO perspective as well.
• Quarkbase: This site offers information primarily tailored towards gauging the popularity of a site from an SEO and social networking point of view.
• Firebug: Firebug is an add-on primarily written for Firefox. While it is chock full of utilities that are invaluable, of particular interest here is the Net panel. This panel has a Network log tab which provides information on the HTTP headers for pages delivered by the site. These headers often provide information about the website as well as its webserver package. The Net panel is also useful in measuring the response times of each and every element being retrieved during the page load.
• Web Developer: This toolbar provides a plethora of information. Within this deluge, we can also access, for e.g., the Response headers served with each page load. The Web Developer toolbar also packs utilities which ease the HTML or CSS validation of a page and its elements.
• Google Chrome Developer Tools: The Chrome browser also provides its own inspection and information utility which contains a tell-tale Network tab. This tab can be used for accessing the response headers for any page as well as timing information for each element in the page.
• Opera Dragonfly: Similarly, Opera also provides a developer panel with a networking section where response headers can be confirmed and response times are catalogued.
• Is this site built with Drupal?: As the name suggests, this site checks a website and informs you if it has been built with the Drupal CMS or not.

If you have any other sites to recommend, please let me know. Please also report dead links.

Hope this helps somebody out there :)