BuiltWith is a technology profiler which lets you know what websites are made of. It’s sort of like a cookbook whose recipes feature solely dishes made with code, php and CSS.
To use it simply type in a website you’re curious about. BuiltWith will then pull up all sorts of interesting stats and details, such as document info, percentage in common with other sites and ranking. Other information you might find useful includes a sites use of analytics and tracking, for example KillerStartups uses Google Analytics and Mybloglog; there’s also a section which identifies any widgets available; next you’ll find info about frameworks, followed by advertising, feeds, and encoding characteristics. On the side panel are links to metrics sites and additional relevant info. Use BuiltWith to get behind the most popular sites.
BuiltWith.com In Their Own Words
‘BuiltWith is a web site profiler tool. Upon looking up a page, BuiltWith returns all the technologies it can find on the page. BuiltWith’s goal is to help developers, researchers and designers find out what technologies pages are using which may help them to decide what technologies to implement themselves.’
Why BuiltWith.com It Might Be A Killer
BuiltWith has compiled some pretty useful info for programmers and designers. A lot of sites will tell you about a site, i.e. what it does, but few give you such detailed info about a site’s build, its elements.
Some Questions About BuiltWith.com
How accurate is BuiltWith? How comprehensive is it? Will they implement more search options? How many people will find it truly useful? 
