A large part of web development is research. Learning how one website works or how it was developed can help lead the direction of another project. Also, while curiousity is bad for kittens, it's fun for the average web worker. Here is a nice article with a few more links for your bag-of-tricks.
How do I contact the owner of a website? How popular is my site on Digg or Delicious? What other websites are hosted on my web server? Is my competitor using WordPress or Drupal? Example.com is loading fast, what is the name of their web hosting company? Is my blog accessible from China or Japan?
If you got questions like these in your mind, here are some of the most useful online tools to help you know each and every detail of any website on the planet.
Here are the list of these tools.
I haven't heard of any of these, but I'm certainly going to check them out immediately. There is a much more detailed description of each one at the linked article. Of course, it is not always possible to find out everything you might like to know about how your favorite website works. Inevitably, if this information is freely available, it can leave certain high-profile sites vulnerable to zero day security issues. Most web masters with any sense will take measures to hide or otherwise obfuscate this information. And this is another reason to keep these tools handy so that you know what other people can learn about your site. To find out more read the full article at labnol.org > internet > tools.